Python 2.4.1 - Release Notes

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What's New in Python 2.4.1 final?

Release date: 30-MAR-2005

Core and builtins

  • Move exception finalisation later in the shutdown process - this fixes the crash seen in bug #1165761


  • SF patch 1167316: fails self-test if run directly.


  • SF patch 1171767: Darwin 8's headers are anal about POSIX compliance, and linking has changed (prebinding is now deprecated, and libcc_dynamic no longer exists). This configure patch makes things right.

What's New in Python 2.4.1c2?

Release date: 17-MAR-2005


  • Fixed decimal operator and comparison methods to return NotImplemented instead of raising a TypeError when interacting with other types. Allows other classes to successfully implement __radd__ style methods.
  • Bug #1163325: Decimal infinities failed to hash. Attempting to hash a NaN raised an InvalidOperation instead of a TypeError.
  • Bug #1160802: can't build Zope on Windows with 2.4.1c1. The MSVCCompiler class in distutils forgot to record that it was initialized, and continued adding redundant entries to the system PATH environment variable until putenv() complained about the size. This only affected building projects with many C extensions, and only on Windows using Microsoft's compiler. This wasn't visible before because a bugfix first included in 2.4.1c1 provoked it (bug #1110478: revert os.environ.update to do putenv again).
  • Bug #1156259: Seeking in codecs.reader was broken, now fixed.


  • Fix the test for socket.getfqdn() in test_socket to also consider the host name returned by socket.gethostname() a valid return value for getfqdn(). Also clarified the wording of docs and docstring that this is the case.

Extensions Modules

  • os.access now supports Unicode path names on non-Win32 systems.

What's New in Python 2.4.1c1?

Release date: 10-MAR-2005

Core and builtins

  • Bug #1155938: new style classes did not verify that __init__() returns None.
  • Bug #723201: Raise a TypeError for passing bad objects to 'L' format.
  • Bug #1124295: the __name__ attribute of file objects was inadvertently made inaccessible in restricted mode.
  • Bug #1074011: closing sys.std{out,err} now causes a flush() and an ferror() call.
  • Bug #1085744: Add missing overflow check to PySequence_Tuple(). Make resize schedule linear (amortized).
  • marshal.dumps() no longer crashes when the optional argument version is provided.

Extension Modules

  • Patches #925152, #1118602: Avoid reading after the end of the buffer in pyexpat.GetInputContext.
  • Patch #1093585: raise a ValueError for negative history items in readline. {remove_history,replace_history}


  • Patch #1075887: Don't require MSVC in distutils if there is nothing to build.
  • Patch #1103407: Properly deal with tarfile iterators when untarring symbolic links on Windows.
  • Patch #1117454: Remove code to special-case cookies without values in LWPCookieJar.
  • Patch #1117339: Add cookielib special name tests.
  • Patch #1112812: Make bsddb/ more friendly for modulefinder.
  • Patch #1121234: Properly cleanup _exit and tkerror commands.
  • Applied a security fix to SimpleXMLRPCserver (PSF-2005-001). This disables recursive traversal through instance attributes, which can be exploited in various ways.
  • Bug #1110478: Revert os.environ.update to do putenv again.
  • Bug #1103844: fix distutils.install.dump_dirs() with negated options.
  • Bug #1067732: wininst --install-script doesn't leave residual files anymore.
  • StringIO.truncate() now correctly adjusts the size attribute. (Bug #951915).
  • The decimal module wouldn't run on builds without threads (Bug #1083645).
  • Bug #1086555: Fix leak in syslog module.
  • atexit.register no longer references the sys module before importing it. (Bug #1083202).
  • and can now be successfully extended or overridden by subclasses. Formerly, the subclassed method would be ignored by the rest of the module. (Bug #1078905).
  • Bug #1076985: codecs.StreamReader.readline() now calls read() only once when a size argument is given. This prevents a buffer overflow in the tokenizer with very long source lines.
  • Bug #1083110: zlib.decompress.flush() would segfault if called immediately after creating the object, without any intervening .decompress() calls.
  • Bug #1149508: textwrap now handles hyphenated numbers (eg. "2004-03-05") correctly.


  • Bug #1158607: Build with --disable-unicode again.
  • term.h is now properly detected again.
  • Check for tzset no longer dependent on tm->tm_zone to exist in the struct (not required by either ISO C nor the UNIX 2 spec). Tests for sanity in tzname when HAVE_TZNAME defined were also defined. Closes bug #1096244. Thanks Gregory Bond.


  • Bug #1076861: The IDLE shortcut is now correct even if the target directory contains a space.
  • Bug #1085208 and similar: The installer does not fail anymore if VBScript is not available on the target machine, not installed properly, or outdated; the MSI package now does not rely on VB anymore.


  • Bug #1091468: make frameworkinstall now works with DESTROOT builds

  • On 10.3 and later extensions are built with -undefined dynamic_lookup. This ensures that extensions can be built in older versions of Python after a newer framework has been installed. In addition, an extension will not accidentally pull in another copy of the Python interpreter.

    On 10.2 and earlier (or if MACOSX_DEPLOYMENT_TARGET is set to a value <= 10.2) extensions are linked directly to the dylib in the framework, in stead of against the framework itself. This ensures that extensions can be built in older versions of Python after a newer framework has been installed.

  • PackageManager and the underlying module have been updated to version 0.5, which greatly simplifies maintenance of the package databases.


  • Remove all latent references for "Macintosh" that referred to semantics for Mac OS 9 and change to reflect the state for OS X. Closes patch #1095802. Thanks Jack Jansen.

What's New in Python 2.4 final?

Release date: 30-NOV-2004

Core and builtins

  • Bug 875692: Improve signal handling, especially when using threads, by forcing an early re-execution of PyEval_EvalFrame() "periodic" code when things_to_do is not cleared by Py_MakePendingCalls().

What's New in Python 2.4 (release candidate 1)

Release date: 18-NOV-2004

Core and builtins

  • Bug 1061968: Fixes in 2.4a3 to address thread bug 1010677 reintroduced the years-old thread shutdown race bug 225673. Numeric history lesson aside, all bugs in all three reports are fixed now.


  • Bug 1052242: If exceptions are raised by an atexit handler function an attempt is made to execute the remaining handlers. The last exception raised is re-raised.
  • doctest's new support for adding pdb.set_trace() calls to doctests was broken in a dramatic but shallow way. Fixed.
  • Bug 1065388: calendar's day_name, day_abbr, month_name, and month_abbr attributes emulate sequences of locale-correct spellings of month and day names. Because the locale can change at any time, the correct spelling is recomputed whenever one of these is indexed. In the worst case, the index may be a slice object, so these recomputed every day or month name each time they were indexed. This is much slower than necessary in the usual case, when the index is just an integer. In that case, only the single spelling needed is recomputed now; and, when the index is a slice object, only the spellings needed by the slice are recomputed now.
  • Patch 1061679: Added __all__ to


  • Bug 1034277 / Patch 1035255: Remove compilation of core against CoreServices and CoreFoundation on OS X. Involved removing PyMac_GetAppletScriptFile() which has no known users. Thanks Bob Ippolito.


  • The PyRange_New() function is deprecated.

What's New in Python 2.4 beta 2?

Release date: 03-NOV-2004


The Python Software Foundation changed the license under which Python is released, to remove Python version numbers. There were no other changes to the license. So, for example, wherever the license for Python 2.3 said "Python 2.3", the new license says "Python". The intent is to make it possible to refer to the PSF license in a more durable way. For example, some people say they're confused by that the Open Source Initiative's entry for the Python Software Foundation License:

says "Python 2.1.1" all over it, wondering whether it applies only to Python 2.1.1.

The official name of the new license is the Python Software Foundation License Version 2.

Core and builtins

  • Bug #1055820 Cyclic garbage collection was not protecting against that calling a live weakref to a piece of cyclic trash could resurrect an insane mutation of the trash if any Python code ran during gc (via running a dead object's __del__ method, running another callback on a weakref to a dead object, or via any Python code run in any other thread that managed to obtain the GIL while a __del__ or callback was running in the thread doing gc). The most likely symptom was "impossible" AttributeEror exceptions, appearing seemingly at random, on weakly referenced objects. The cure was to clear all weakrefs to unreachable objects before allowing any callbacks to run.
  • Bug #1054139 _PyString_Resize() now invalidates its cached hash value.

Extension Modules

  • Bug #1048870: the compiler now generates distinct code objects for functions with identical bodies. This was producing confusing traceback messages which pointed to the function where the code object was first defined rather than the function being executed.


  • Patch #1056967 changes the semantics of Template.safe_substitute() so that no ValueError is raised on an 'invalid' match group. Now the delimiter is returned.
  • Bug #1052503 pdb.runcall() was not passing along keyword arguments.
  • Bug #902037: XML.sax.saxutils.prepare_input_source() now combines relative paths with a base path before checking os.path.isfile().
  • The whichdb module can now be run from the command line.
  • Bug #1045381: time.strptime() can now infer the date using %U or %W (week of the year) when the day of the week and year are also specified.
  • Bug #1048816: fix bug in Ctrl-K at start of line in curses.textpad.Textbox
  • Bug #1017553: fix bug in tarfile.filemode()
  • Patch #737473: fix bug that old source code is shown in tracebacks even if the source code is updated and reloaded.


  • Patch #1044395: --enable-shared is allowed in FreeBSD also.

What's New in Python 2.4 beta 1?

Release date: 15-OCT-2004

Core and builtins

  • Patch #975056: Restartable signals were not correctly disabled on BSD systems. Consistently use PyOS_setsig() instead of signal().
  • The internal portable implementation of thread-local storage (TLS), used by the PyGILState_Ensure()/PyGILState_Release() API, was not thread-correct. This could lead to a variety of problems, up to and including segfaults. See bug 1041645 for an example.
  • Added a command line option, -m module, which searches sys.path for the module and then runs it. (Contributed by Nick Coghlan.)
  • The bytecode optimizer now folds tuples of constants into a single constant.
  • SF bug #513866: Float/long comparison anomaly. Prior to 2.4b1, when an integer was compared to a float, the integer was coerced to a float. That could yield spurious overflow errors (if the integer was very large), and to anomalies such as long(1e200)+1 == 1e200 == long(1e200)-1. Coercion to float is no longer performed, and cases like long(1e200)-1 < 1e200, long(1e200)+1 > 1e200 and (1 << 20000) > 1e200 are computed correctly now.

Extension modules

  • collections.deque objects didn't play quite right with garbage collection, which could lead to a segfault in a release build, or an assert failure in a debug build. Also, added overflow checks, better detection of mutation during iteration, and shielded deque comparisons from unusual subclass overrides of the __iter__() method.


  • Patch 1046644: distutils build_ext grew two new options - --swig for specifying the swig executable to use, and --swig-opts to specify options to pass to swig. --swig-opts="-c++" is the new way to spell --swig-cpp.
  • Patch 983206: distutils now obeys environment variable LDSHARED, if it is set.
  • Added Peter Astrand's module. See PEP 324 for details.
  • time.strptime() now properly escapes timezones and all other locale-specific strings for regex-specific symbols. Was breaking under Japanese Windows when the timezone was specified as "Tokyo (standard time)". Closes bug #1039270.
  • Updates for the email package:
    • email.Utils.formatdate() grew a 'usegmt' argument for HTTP support.
    • All deprecated APIs that in email 2.x issued warnings have been removed: _encoder argument to the MIMEText constructor, Message.add_payload(), Utils.dump_address_pair(), Utils.decode(), Utils.encode()
    • New deprecations: Generator.__call__(), Message.get_type(), Message.get_main_type(), Message.get_subtype(), the 'strict' argument to the Parser constructor. These will be removed in email 3.1.
    • Support for Python earlier than 2.3 has been removed (see PEP 291).
    • All defect classes have been renamed to end in 'Defect'.
    • Some FeedParser fixes; also a MultipartInvariantViolationDefect will be added to messages that claim to be multipart but really aren't.
    • Updates to documentation.
  • re's findall() and finditer() functions now take an optional flags argument just like the compile(), search(), and match() functions. Also, documented the previously existing start and stop parameters for the findall() and finditer() methods of regular expression objects.
  • rfc822 Messages now support iterating over the headers.
  • The (undocumented) tarfile.Tarfile.membernames has been removed; applications should use the getmember function.
  • httplib now offers symbolic constants for the HTTP status codes.
  • SF bug #1028306: Trying to compare a to a datetime.datetime mistakenly compared only the year, month and day. Now it acts like a mixed-type comparison: False for ==, True for !=, and raises TypeError for other comparison operators. Because datetime is a subclass of date, comparing only the base class (date) members can still be done, if that's desired, by forcing using of the appropriate date method; e.g., a_date.__eq__(a_datetime) is true if and only if the year, month and day members of a_date and a_datetime are equal.
  • bdist_rpm now supports command line options --force-arch, {pre,post}-install, {pre,post}-uninstall, and {prep,build,install,clean,verify}-script.
  • SF patch #998993: The UTF-8 and the UTF-16 stateful decoders now support decoding incomplete input (when the input stream is temporarily exhausted). codecs.StreamReader now implements buffering, which enables proper readline support for the UTF-16 decoders. has a new argument chars which specifies the number of characters to return. codecs.StreamReader.readline() and codecs.StreamReader.readlines() have a new argument keepends. Trailing "n"s will be stripped from the lines if keepends is false.
  • The documentation for doctest is greatly expanded, and now covers all the new public features (of which there are many).
  • doctest.master was put back in, and doctest.testmod() once again updates it. This isn't good, because every testmod() call contributes to bloating the "hidden" state of doctest.master, but some old code apparently relies on it. For now, all we can do is encourage people to stitch doctests together via doctest's unittest integration features instead.
  • httplib now handles ipv6 address/port pairs.
  • SF bug #1017864: ConfigParser now correctly handles default keys, processing them with ConfigParser.optionxform when supplied, consistent with the handling of config file entries and runtime-set options.
  • SF bug #997050: Document, test, & check for non-string values in ConfigParser. Moved the new string-only restriction added in rev. 1.65 to the SafeConfigParser class, leaving existing ConfigParser & RawConfigParser behavior alone, and documented the conditions under which non-string values work.


  • Building on darwin now includes /opt/local/include and /opt/local/lib for building extension modules. This is so as to include software installed as a DarwinPorts port <>
  • pyport.h now defines a Py_IS_NAN macro. It works as-is when the platform C computes true for x != x if and only if X is a NaN. Other platforms can override the default definition with a platform- specific spelling in that platform's pyconfig.h. You can also override pyport.h's default Py_IS_INFINITY definition now.


  • SF patch 1044089: New function PyEval_ThreadsInitialized() returns non-zero if PyEval_InitThreads() has been called.
  • The undocumented and unused extern int _PyThread_Started was removed.
  • The C API calls PyInterpreterState_New() and PyThreadState_New() are two of the very few advertised as being safe to call without holding the GIL. However, this wasn't true in a debug build, as bug 1041645 demonstrated. In a debug build, Python redirects the PyMem family of calls to Python's small-object allocator, to get the benefit of its extra debugging capabilities. But Python's small-object allocator isn't threadsafe, relying on the GIL to avoid the expense of doing its own locking. PyInterpreterState_New() and PyThreadState_New() call the platform malloc() directly now, regardless of build type.
  • PyLong_AsUnsignedLong[Mask] now support int objects as well.
  • SF patch #998993: PyUnicode_DecodeUTF8Stateful and PyUnicode_DecodeUTF16Stateful have been added, which implement stateful decoding.


  • test__locale ported to unittest


  • plistlib now supports non-dict root objects. There is also a new interface for reading and writing plist files: readPlist(pathOrFile) and writePlist(rootObject, pathOrFile)


  • The text file comparison scripts and now read the input files in universal-newline mode. This spares them from consuming a great deal of time to deduce the useless result that, e.g., a file with Windows line ends and a file with Linux line ends have no lines in common.

What's New in Python 2.4 alpha 3?

Release date: 02-SEP-2004

Core and builtins

  • SF patch #1007189: from ... import ... statements now allow the name list to be surrounded by parentheses.
  • Some speedups for long arithmetic, thanks to Trevor Perrin. Gradeschool multiplication was sped a little by optimizing the C code. Gradeschool squaring was sped by about a factor of 2, by exploiting that about half the digit products are duplicates in a square. Because exponentiation uses squaring often, this also speeds long power. For example, the time to compute 17**1000000 dropped from about 14 seconds to 9 on my box due to this much. The cutoff for Karatsuba multiplication was raised, since gradeschool multiplication got quicker, and the cutoff was aggressively small regardless. The exponentiation algorithm was switched from right-to-left to left-to-right, which is more efficient for small bases. In addition, if the exponent is large, the algorithm now does 5 bits (instead of 1 bit) at a time. That cut the time to compute 17**1000000 on my box in half again, down to about 4.5 seconds.
  • OverflowWarning is no longer generated. PEP 237 scheduled this to occur in Python 2.3, but since OverflowWarning was disabled by default, nobody realized it was still being generated. On the chance that user code is still using them, the Python builtin OverflowWarning, and corresponding C API PyExc_OverflowWarning, will exist until Python 2.5.
  • Py_InitializeEx has been added.
  • Fix the order of application of decorators. The proper order is bottom-up; the first decorator listed is the last one called.
  • SF patch #1005778. Fix a seg fault if the list size changed while calling list.index(). This could happen if a rich comparison function modified the list.
  • The func_name (a.k.a. __name__) attribute of user-defined functions is now writable.
  • code_new (a.k.a new.code()) now checks its arguments sufficiently carefully that passing them on to PyCode_New() won't trigger calls to Py_FatalError() or PyErr_BadInternalCall(). It is still the case that the returned code object might be entirely insane.
  • Subclasses of string can no longer be interned. The semantics of interning were not clear here -- a subclass could be mutable, for example -- and had bugs. Explicitly interning a subclass of string via intern() will raise a TypeError. Internal operations that attempt to intern a string subclass will have no effect.
  • Bug 1003935: xrange() could report bogus OverflowErrors. Documented what xrange() intends, and repaired tests accordingly.

Extension modules

  • difflib now supports HTML side-by-side diff.
  • os.urandom has been added for systems that support sources of random data.
  • Patch 1012740: truncate() on a writable cStringIO now resets the position to the end of the stream. This is consistent with the original StringIO module and avoids inadvertently resurrecting data that was supposed to have been truncated away.
  • Added socket.socketpair().
  • Added CurrentByteIndex, CurrentColumnNumber, CurrentLineNumber members to xml.parsers.expat.XMLParser object.
  • The mpz, rotor, and xreadlines modules, all deprecated in earlier versions of Python, have now been removed.


  • Patch #934356: if a module defines __all__, believe that rather than using heuristics for filtering out imported names.
  • Patch #941486: added os.path.lexists(), which returns True for broken symlinks, unlike os.path.exists().
  • the random module now uses os.urandom() for seeding if it is available. Added a new generator based on os.urandom().
  • difflib and can now generate HTML.
  • bdist_rpm now includes version and release in the BuildRoot, and replaces - by _ in version and release.
  • distutils build/build_scripts now has an -e option to specify the path to the Python interpreter for installed scripts.
  • PEP 292 classes Template and SafeTemplate are added to the string module.
  • tarfile now generates GNU tar files by default.
  • HTTPResponse has now a getheaders method.
  • Patch #1006219: let inspect.getsource handle '@' decorators. Thanks Simon Percivall.
  • logging.handlers.SMTPHandler.date_time has been removed; the class now uses email.Utils.formatdate to generate the time stamp.
  • A new function tkFont.nametofont was added to return an existing font. The Font class constructor now has an additional exists argument which, if True, requests to return/configure an existing font, rather than creating a new one.
  • Updated the decimal package's min() and max() methods to match the latest revision of the General Decimal Arithmetic Specification. Quiet NaNs are ignored and equal values are sorted based on sign and exponent.
  • The decimal package's Context.copy() method now returns deep copies.
  • Deprecated sys.exitfunc in favor of the atexit module. The sys.exitfunc attribute will be kept around for backwards compatibility and atexit will just become the one preferred way to do it.
  • patch #675551: Add get_history_item and replace_history_item functions to the readline module.
  • bug #989672: pdb.doc and the help messages for the help_d and help_u methods of the pdb.Pdb class gives have been corrected. d(own) goes to a newer frame, u(p) to an older frame, not the other way around.
  • bug #990669: os.path.realpath() will resolve symlinks before normalizing the path, as normalizing the path may alter the meaning of the path if it contains symlinks.
  • bug #851123: shutil.copyfile will raise an exception when trying to copy a file onto a link to itself. Thanks Gregory Ball.
  • bug #570300: Fix inspect to resolve file locations using os.path.realpath() so as to properly list all functions in a module when the module itself is reached through a symlink. Thanks Johannes Gijsbers.
  • doctest refactoring continued. See the docs for details. As part of this effort, some old and little- (never?) used features are now deprecated: the Tester class, the module is_private() function, and the isprivate argument to testmod(). The Tester class supplied a feeble "by hand" way to combine multiple doctests, if you knew exactly what you were doing. The newer doctest features for unittest integration already did a better job of that, are stronger now than ever, and the new DocTestRunner class is a saner foundation if you want to do it by hand. The "private name" filtering gimmick was a mistake from the start, and testmod() changed long ago to ignore it by default. If you want to filter out tests, the new DocTestFinder class can be used to return a list of all doctests, and you can filter that list by any computable criteria before passing it to a DocTestRunner instance.
  • Bug #891637, patch #1005466: fix inspect.getargs() crash on def foo((bar)).


  • IDLE's shortcut keys for windows are now case insensitive so that Control-V works the same as Control-v.
  • Generate POT-Creation-Date header in ISO format.


  • Backward incompatibility: longintrepr.h now triggers a compile-time error if SHIFT (the number of bits in a Python long "digit") isn't divisible by 5. This new requirement allows simple code for the new 5-bits-at-a-time long_pow() implementation. If necessary, the restriction could be removed (by complicating long_pow(), or by falling back to the 1-bit-at-a-time algorithm), but there are no plans to do so.
  • bug #991962: When building with --disable-toolbox-glue on Darwin no attempt to build Mac-specific modules occurs.
  • The --with-tsc flag to configure to enable VM profiling with the processor's timestamp counter now works on PPC platforms.
  • patch #1006629: Define _XOPEN_SOURCE to 500 on Solaris 8/9 to match GCC's definition and avoid redefinition warnings.
  • Detect pthreads support (provided by gnu pth pthread emulation) on GNU/k*BSD systems.
  • bug #1005737, #1007249: Fixed several build problems and warnings found on old/legacy C compilers of HP-UX, IRIX and Tru64.



  • patch #1005936, bug #1009373: fix index entries which contain an underscore when viewed with Acrobat.
  • bug #990669: os.path.normpath may alter the meaning of a path if it contains symbolic links. This has been documented in a comment since 1992, but is now in the library reference as well.

New platforms

  • FreeBSD 6 is now supported.



  • Boosted the stack reservation for python.exe and pythonw.exe from the default 1MB to 2MB. Stack frames under VC 7.1 for 2.4 are enough bigger than under VC 6.0 for 2.3.4 that deeply recursive progams within the default sys.getrecursionlimit() default value of 1000 were able to suffer undetected C stack overflows. The standard test program test_compiler was one such program. If a Python process on Windows "just vanishes" without a trace, and without an error message of any kind, but with an exit code of 128, undetected stack overflow may be the problem.


What's New in Python 2.4 alpha 2?

Release date: 05-AUG-2004

Core and builtins

  • Patch #980695: Implements efficient string concatenation for statements of the form s=s+t and s+=t. This will vary across implementations. Accordingly, the str.join() method is strongly preferred for performance sensitive code.

  • PEP-0318, Function Decorators have been added to the language. These are implemented using the Java-style @decorator syntax, like so:

    def foo(bar):

    (The PEP needs to be updated to reflect the current state)

  • When importing a module M raises an exception, Python no longer leaves M in sys.modules. Before 2.4a2 it did, and a subsequent import of M would succeed, picking up a module object from sys.modules reflecting as much of the initialization of M as completed before the exception was raised. Subsequent imports got no indication that M was in a partially- initialized state, and the importers could get into arbitrarily bad trouble as a result (the M they got was in an unintended state, arbitrarily far removed from M's author's intent). Now subsequent imports of M will continue raising exceptions (but if, for example, the source code for M is edited between import attempts, then perhaps later attempts will succeed, or raise a different exception).

    This can break existing code, but in such cases the code was probably working before by accident. In the Python source, the only case of breakage discovered was in a test accidentally relying on a damaged module remaining in sys.modules. Cases are also known where tests deliberately provoking import errors remove damaged modules from sys.modules themselves, and such tests will break now if they do an unconditional del sys.modules[M].

  • u'%s' % obj will now try obj.__unicode__() first and fallback to obj.__str__() if no __unicode__ method can be found.

  • Patch #550732: Add PyArg_VaParseTupleAndKeywords(). Analogous to PyArg_VaParse(). Both are now documented. Thanks Greg Chapman.

  • Allow string and unicode return types from .encode()/.decode() methods on string and unicode objects. Added unicode.decode() which was missing for no apparent reason.

  • An attempt to fix the mess that is Python's behaviour with signal handlers and threads, complicated by readline's behaviour. It's quite possible that there are still bugs here.

  • Added C macros Py_CLEAR and Py_VISIT to ease the implementation of types that support garbage collection.

  • Compiler now treats None as a constant.

  • The type of values returned by __int__, __float__, __long__, __oct__, and __hex__ are now checked. Returning an invalid type will cause a TypeError to be raised. This matches the behavior of Jython.

  • Implemented bind_textdomain_codeset() in locale module.

  • Added a workaround for proper string operations in BSDs. str.split and* methods can now work correctly with UTF-8 locales.

  • Bug #989185: unicode.iswide() and unicode.width() is dropped and the East Asian Width support is moved to unicodedata extension module.

  • Patch #941229: The source code encoding in interactive mode now refers sys.stdin.encoding not just ISO-8859-1 anymore. This allows for non-latin-1 users to write unicode strings directly.

Extension modules

  • cpickle now supports the same keyword arguments as pickle.


  • Added new codecs and aliases for ISO_8859-11, ISO_8859-16 and TIS-620

  • Thanks to Edward Loper, doctest has been massively refactored, and many new features were added. Full docs will appear later. For now the doctest module comments and new test cases give good coverage. The refactoring provides many hook points for customizing behavior (such as how to report errors, and how to compare expected to actual output). New features include a <BLANKLINE> marker for expected output containing blank lines, options to produce unified or context diffs when actual output doesn't match expectations, an option to normalize whitespace before comparing, and an option to use an ellipsis to signify "don't care" regions of output.

  • Tkinter now supports the wish -sync and -use options.

  • The following methods in time support passing of None: ctime(), gmtime(), and localtime(). If None is provided, the current time is used (the same as when the argument is omitted). [SF bug 658254, patch 663482]

  • nntplib does now allow to ignore a .netrc file.

  • urllib2 now recognizes Basic authentication even if other authentication schemes are offered.

  • Bug #1001053. now accepts unicode filenames.

  • gzip.GzipFile has a new fileno() method, to retrieve the handle of the underlying file object (provided it has a fileno() method). This is needed if you want to use os.fsync() on a GzipFile.

  • imaplib has two new methods: deleteacl and myrights.

  • nntplib has two new methods: description and descriptions. They use a more RFC-compliant way of getting a newsgroup description.

  • Bug #993394. Fix a possible red herring of KeyError in 'threading' being raised during interpreter shutdown from a registered function with atexit when dummy_threading is being used.

  • Bug #857297/Patch #916874. Fix an error when extracting a hard link from a tarfile.

  • Patch #846659. Fix an error in when using GNU longname/longlink creation.

  • The obsolete has been deleted. The builtin fcntl module has been available (on platforms that support fcntl) since Python 1.5a3, and all did is export fcntl's names, after generating a deprecation warning telling you to use fcntl directly.

  • Several new unicode codecs are added: big5hkscs, euc_jis_2004, iso2022_jp_2004, shift_jis_2004.

  • Bug #788520. Queue.{get, get_nowait, put, put_nowait} have new implementations, exploiting Conditions (which didn't exist at the time Queue was introduced). A minor semantic change is that the Full and Empty exceptions raised by non-blocking calls now occur only if the queue truly was full or empty at the instant the queue was checked (of course the Queue may no longer be full or empty by the time a calling thread sees those exceptions, though). Before, the exceptions could also be raised if it was "merely inconvenient" for the implementation to determine the true state of the Queue (because the Queue was locked by some other method in progress).

  • Bugs #979794 and #980117: difflib.get_grouped_opcodes() now handles the case of comparing two empty lists. This affected both context_diff() and unified_diff(),

  • Bug #980938: smtplib now prints debug output to sys.stderr.

  • Bug #930024: posixpath.realpath() now handles infinite loops in symlinks by returning the last point in the path that was not part of any loop. Thanks AM Kuchling.

  • Bug #980327: ntpath not handles compressing erroneous slashes between the drive letter and the rest of the path. Also clearly handles UNC addresses now as well. Thanks Paul Moore.

  • bug #679953: should now work for files over 2 GB. The packed data for file sizes (compressed and uncompressed) was being stored as signed instead of unsigned.

  • now only uses signals in the IBM spec. The other conditions are no longer part of the public API.

  • codecs module now has two new generic APIs: encode() and decode() which don't restrict the return types (unlike the unicode and string methods of the same name).

  • Non-blocking SSL sockets work again; they were broken in Python 2.3. SF patch 945642.

  • doctest unittest integration improvements:

    o Improved the unitest test output for doctest-based unit tests

    o Can now pass setUp and tearDown functions when creating


  • The threading module has a new class, local, for creating objects that provide thread-local data.

  • Bug #990307: when keep_empty_values is True, cgi.parse_qsl() no longer returns spurious empty fields.

  • Implemented bind_textdomain_codeset() in gettext module.

  • Introduced in gettext module the l*gettext() family of functions, which return translation strings encoded in the preferred encoding, as informed by locale module's getpreferredencoding().

  • optparse module (and tests) upgraded to Optik 1.5a1. Changes:

    • Add expansion of default values in help text: the string "%default" in an option's help string is expanded to str() of that option's default value, or "none" if no default value.
    • Bug #955889: option default values that happen to be strings are now processed in the same way as values from the command line; this allows generation of nicer help when using custom types. Can be disabled with parser.set_process_default_values(False).
    • Bug #960515: don't crash when generating help for callback options that specify 'type', but not 'dest' or 'metavar'.
    • Feature #815264: change the default help format for short options that take an argument from e.g. "-oARG" to "-o ARG"; add set_short_opt_delimiter() and set_long_opt_delimiter() methods to HelpFormatter to allow (slight) customization of the formatting.
    • Patch #736940: internationalize Optik: all built-in user- targeted literal strings are passed through gettext.gettext(). (If you want translations (.po files), they're not included with Python -- you'll find them in the Optik source distribution from .)
    • Bug #878453: respect $COLUMNS environment variable for wrapping help output.
    • Feature #988122: expand "%prog" in the 'description' passed to OptionParser, just like in the 'usage' and 'version' strings. (This is not done in the 'description' passed to OptionGroup.)


  • PyImport_ExecCodeModule() and PyImport_ExecCodeModuleEx(): if an error occurs while loading the module, these now delete the module's entry from sys.modules. All ways of loading modules eventually call one of these, so this is an error-case change in semantics for all ways of loading modules. In rare cases, a module loader may wish to keep a module object in sys.modules despite that the module's code cannot be executed. In such cases, the module loader must arrange to reinsert the name and module object in sys.modules. PyImport_ReloadModule() has been changed to reinsert the original module object into sys.modules if the module reload fails, so that its visible semantics have not changed.
  • A large pile of datetime field-extraction macros is now documented, thanks to Anthony Tuininga (patch #986010).


  • Improved the tutorial on creating types in C.
    • point out the importance of reassigning data members before assigning their values
    • correct my misconception about return values from visitprocs. Sigh.
    • mention the labor saving Py_VISIT and Py_CLEAR macros.
  • Major rewrite of the math module docs, to address common confusions.


  • The test data files for the decimal test suite are now installed on platforms that use the Makefile.
  • SF patch 995225: The test file testtar.tar accidentally contained CVS keywords (like $Id: NEWS.txt,v 1.3 2005/03/30 09:06:13 anthony Exp $), which could cause spurious failures in depending on how the test file was checked out.

What's New in Python 2.4 alpha 1?

Release date: 08-JUL-2004

Core and builtins

  • weakref.ref is now the type object also known as weakref.ReferenceType; it can be subclassed like any other new-style class. There's less per-entry overhead in WeakValueDictionary objects now (one object instead of three).
  • Bug #951851: Python crashed when reading import table of certain Windows DLLs.
  • Bug #215126. The locals argument to eval(), execfile(), and exec now accept any mapping type.
  • marshal now shares interned strings. This change introduces a new .pyc magic.
  • Bug #966623. classes created with type() in an exec(, {}) don't have a __module__, but code in typeobject assumed it would always be there.
  • Python no longer relies on the LC_NUMERIC locale setting to be the "C" locale; as a result, it no longer tries to prevent changing the LC_NUMERIC category.
  • Bug #952807: Unpickling pickled instances of subclasses of, datetime.datetime and datetime.time could yield insane objects. Thanks to Jiwon Seo for a fix.
  • Bug #845802: Python crashes when is a directory.
  • Unicode objects received two new methods: iswide() and width(). These query East Asian width information, as specified in Unicode TR11.
  • Improved the tuple hashing algorithm to give fewer collisions in common cases. Fixes bug #942952.
  • Implemented generator expressions (PEP 289). Coded by Jiwon Seo.
  • Enabled the profiling of C extension functions (and builtins) - check new documentation and modified profile and bdb modules for more details
  • Set to the object passed to open (instead of a new string)
  • Moved tracebackobject into traceback.h and renamed to PyTracebackObject
  • Optimized the byte coding for multiple assignments like "a,b=b,a" and "a,b,c=1,2,3". Improves their speed by 25% to 30%.
  • Limit the nested depth of a tuple for the second argument to isinstance() and issubclass() to the recursion limit of the interpreter. Fixes bug #858016 .
  • Optimized dict iterators, creating separate types for each and having them reveal their length. Also optimized the methods: keys(), values(), and items().
  • Implemented a newcode opcode, LIST_APPEND, that simplifies the generated bytecode for list comprehensions and further improves their performance (about 35%).
  • Implemented rich comparisons for floats, which seems to make comparisons involving NaNs somewhat less surprising when the underlying C compiler actually implements C99 semantics.
  • Optimized list.extend() to save memory and no longer create intermediate sequences. Also, extend() now pre-allocates the needed memory whenever the length of the iterable is known in advance -- this halves the time to extend the list.
  • Optimized list resize operations to make fewer calls to the system realloc(). Significantly speeds up list appends, list pops, list comprehensions, and the list constructor (when the input iterable length is not known).
  • Changed the internal list over-allocation scheme. For larger lists, overallocation ranged between 3% and 25%. Now, it is a constant 12%. For smaller lists (n<8), overallocation was up to eight elements. Now, the overallocation is no more than three elements -- this improves space utilization for applications that have large numbers of small lists.
  • Most list bodies now get re-used rather than freed. Speeds up list instantiation and deletion by saving calls to malloc() and free().
  • The dict.update() method now accepts all the same argument forms as the dict() constructor. This now includes item lists and/or keyword arguments.
  • Support for arbitrary objects supporting the read-only buffer interface as the co_code field of code objects (something that was only possible to create from C code) has been removed.
  • Made omitted callback and None equivalent for weakref.ref() and weakref.proxy(); the None case wasn't handled correctly in all cases.
  • Fixed problem where PyWeakref_NewRef() and PyWeakref_NewProxy() assumed that initial existing entries in an object's weakref list would not be removed while allocating a new weakref object. Since GC could be invoked at that time, however, that assumption was invalid. In a truly obscure case of GC being triggered during creation for a new weakref object for an referent which already has a weakref without a callback which is only referenced from cyclic trash, a memory error can occur. This consistently created a segfault in a debug build, but provided less predictable behavior in a release build.
  • input() builtin function now respects compiler flags such as __future__ statements. SF patch 876178.
  • Removed PendingDeprecationWarning from apply(). apply() remains deprecated, but the nuisance warning will not be issued.
  • At Python shutdown time (Py_Finalize()), 2.3 called cyclic garbage collection twice, both before and after tearing down modules. The call after tearing down modules has been disabled, because too much of Python has been torn down then for __del__ methods and weakref callbacks to execute sanely. The most common symptom was a sequence of uninformative messages on stderr when Python shut down, produced by threads trying to raise exceptions, but unable to report the nature of their problems because too much of the sys module had already been destroyed.
  • Removed FutureWarnings related to hex/oct literals and conversions and left shifts. (Thanks to Kalle Svensson for SF patch 849227.) This addresses most of the remaining semantic changes promised by PEP 237, except for repr() of a long, which still shows the trailing 'L'. The PEP appears to promise warnings for operations that changed semantics compared to Python 2.3, but this is not implemented; we've suffered through enough warnings related to hex/oct literals and I think it's best to be silent now.
  • For str and unicode objects, the ljust(), center(), and rjust() methods now accept an optional argument specifying a fill character other than a space.
  • When method objects have an attribute that can be satisfied either by the function object or by the method object, the function object's attribute usually wins. Christian Tismer pointed out that that this is really a mistake, because this only happens for special methods (like __reduce__) where the method object's version is really more appropriate than the function's attribute. So from now on, all method attributes will have precedence over function attributes with the same name.
  • Critical bugfix, for SF bug 839548: if a weakref with a callback, its callback, and its weakly referenced object, all became part of cyclic garbage during a single run of garbage collection, the order in which they were torn down was unpredictable. It was possible for the callback to see partially-torn-down objects, leading to immediate segfaults, or, if the callback resurrected garbage objects, to resurrect insane objects that caused segfaults (or other surprises) later. In one sense this wasn't surprising, because Python's cyclic gc had no knowledge of Python's weakref objects. It does now. When weakrefs with callbacks become part of cyclic garbage now, those weakrefs are cleared first. The callbacks don't trigger then, preventing the problems. If you need callbacks to trigger, then just as when cyclic gc is not involved, you need to write your code so that weakref objects outlive the objects they weakly reference.
  • Critical bugfix, for SF bug 840829: if cyclic garbage collection happened to occur during a weakref callback for a new-style class instance, subtle memory corruption was the result (in a release build; in a debug build, a segfault occurred reliably very soon after). This has been repaired.
  • Compiler flags set in PYTHONSTARTUP are now active in __main__.
  • Added two builtin types, set() and frozenset().
  • Added a reversed() builtin function that returns a reverse iterator over a sequence.
  • Added a sorted() builtin function that returns a new sorted list from any iterable.
  • CObjects are now mutable (on the C level) through PyCObject_SetVoidPtr.
  • list.sort() now supports three keyword arguments: cmp, key, and reverse. The key argument can be a function of one argument that extracts a comparison key from the original record: mylist.sort(key=str.lower). The reverse argument is a boolean value and if True will change the sort order as if the comparison arguments were reversed. In addition, the documentation has been amended to provide a guarantee that all sorts starting with Py2.3 are guaranteed to be stable (the relative order of records with equal keys is unchanged).
  • Added test whether wchar_t is signed or not. A signed wchar_t is not usable as internal unicode type base for Py_UNICODE since the unicode implementation assumes an unsigned type.
  • Fixed a bug in the cache of length-one Unicode strings that could lead to a seg fault. The specific problem occurred when an earlier, non-fatal error left an uninitialized Unicode object in the freelist.
  • The % formatting operator now supports '%F' which is equivalent to '%f'. This has always been documented but never implemented.
  • complex(obj) could leak a little memory if obj wasn't a string or number.
  • zip() with no arguments now returns an empty list instead of raising a TypeError exception.
  • obj.__contains__() now returns True/False instead of 1/0. SF patch 820195.
  • Python no longer tries to be smart about recursive comparisons. When comparing containers with cyclic references to themselves it will now just hit the recursion limit. See SF patch 825639.
  • str and unicode builtin types now have an rsplit() method that is same as split() except that it scans the string from the end working towards the beginning. See SF feature request 801847.
  • Fixed a bug in object.__reduce_ex__ when using protocol 2. Failure to clear the error when attempts to get the __getstate__ attribute fail caused intermittent errors and odd behavior.
  • buffer objects based on other objects no longer cache a pointer to the data and the data length. Instead, the appropriate tp_as_buffer method is called as necessary.
  • fixed: if a file is opened with an explicit buffer size >= 1, repeated close() calls would attempt to free() the buffer already free()ed on the first call.

Extension modules

  • Added socket.getservbyport(), and make the second argument in getservbyname() and getservbyport() optional.
  • time module code that deals with input POSIX timestamps will now raise ValueError if more than a second is lost in precision when the timestamp is cast to the platform C time_t type. There's no chance that the platform will do anything sensible with the result in such cases. This includes ctime(), localtime() and gmtime(). Assorted fromtimestamp() and utcfromtimestamp() methods in the datetime module were also protected. Closes bugs #919012 and 975996.
  • fcntl.ioctl now warns if the mutate flag is not specified.
  • nt now properly allows to refer to UNC roots, e.g. in nt.stat().
  • the weakref module now supports additional objects: array.array, sre.pattern_objects, file objects, and sockets.
  • operator.isMappingType() and operator.isSequenceType() now give fewer false positives.
  • socket.sslerror is now a subclass of socket.error . Also added socket.error to the socket module's C API.
  • Bug #920575: A problem where the _locale module segfaults on nl_langinfo(ERA) caused by GNU libc's illegal NULL return is fixed.
  • array objects now support the copy module. Also, their resizing scheme has been updated to match that used for list objects. This improves the performance (speed and memory usage) of append() operations. Also, array.array() and array.extend() now accept any iterable argument for repeated appends without needing to create another temporary array.
  • cStringIO.writelines() now accepts any iterable argument and writes the lines one at a time rather than joining them and writing once. Made a parallel change to StringIO.writelines(). Saves memory and makes suitable for use with generator expressions.
  • time.strftime() now checks that the values in its time tuple argument are within the proper boundaries to prevent possible crashes from the platform's C library implementation of strftime(). Can possibly break code that uses values outside the range that didn't cause problems previously (such as sitting day of year to 0). Fixes bug #897625.
  • The socket module now supports Bluetooth sockets, if the system has <bluetooth/bluetooth.h>
  • Added a collections module containing a new datatype, deque(), offering high-performance, thread-safe, memory friendly appends and pops on either side of the deque.
  • Several modules now take advantage of collections.deque() for improved performance: Queue, mutex, shlex, threading, and pydoc.
  • The operator module has two new functions, attrgetter() and itemgetter() which are useful for creating fast data extractor functions for map(), list.sort(), itertools.groupby(), and other functions that expect a function argument.
  • socket.SHUT_{RD,WR,RDWR} was added.
  • os.getsid was added.
  • The pwd module incorrectly advertised its struct type as struct_pwent; this has been renamed to struct_passwd. (The old name is still supported for backwards compatibility.)
  • The xml.parsers.expat module now provides Expat 1.95.7.
  • socket.IPPROTO_IPV6 was added.
  • readline.clear_history was added.
  • now accepts sequences for its first three arguments.
  • cStringIO now supports the f.closed attribute.
  • The signal module now exposes SIGRTMIN and SIGRTMAX (if available).
  • curses module now supports use_default_colors(). [patch #739124]
  • Bug #811028: ncurses.h breakage on FreeBSD/MacOS X
  • Bug #814613: INET_ADDRSTRLEN fix needed for all compilers on SGI
  • Implemented non-recursive SRE matching scheme (#757624).
  • Implemented (?(id/name)yes|no) support in SRE (#572936).
  • random.seed() with no arguments or None uses time.time() as a default seed. Modified to match Py2.2 behavior and use fractional seconds so that successive runs are more likely to produce different sequences.
  • random.Random has a new method, getrandbits(k), which returns an int with k random bits. This method is now an optional part of the API for user defined generators. Any generator that defines genrandbits() can now use randrange() for ranges with a length >= 2**53. Formerly, randrange would return only even numbers for ranges that large (see SF bug #812202). Generators that do not define genrandbits() now issue a warning when randrange() is called with a range that large.
  • itertools has a new function, groupby() for aggregating iterables into groups sharing the same key (as determined by a key function). It offers some of functionality of SQL's groupby keyword and of the Unix uniq filter.
  • itertools now has a new tee() function which produces two independent iterators from a single iterable.
  • itertools.izip() with no arguments now returns an empty iterator instead of raising a TypeError exception.
  • Fixed #853061: allow BZ2Compressor.compress() to receive an empty string as parameter.


  • Bug #981530: Fix UnboundLocalError in shutil.rmtree(). This affects the documented behavior: the function passed to the onerror() handler can now also be os.listdir.
  • Bug #754449: threading.Thread objects no longer mask exceptions raised during interpreter shutdown with another exception from attempting to handle the original exception.
  • Added per PEP 327.
  • Bug #981299: rsync is now a recognized protocol in urlparse that uses a "netloc" portion of a URL.
  • Bug #919012: shutil.move() will not try to move a directory into itself. Thanks Johannes Gijsbers.
  • Bug #934282: pydoc.stripid() is now case-insensitive. Thanks Robin Becker.
  • Bug #823209: cmath.log() now takes an optional base argument so that its API matches math.log().
  • Bug #957381: distutils bdist_rpm no longer fails on recent RPM versions that generate a -debuginfo.rpm
  • os.path.devnull has been added for all supported platforms.
  • Fixed #877165: distutils now picks the right C++ compiler command on cygwin and mingw32.
  • urllib.urlopen().readline() now handles HTTP/0.9 correctly.
  • refactored into functions. Also wrote regression tests for the module.
  • The distutils install command now supports the --home option and installation scheme for all platforms.
  • asyncore.loop now has a repeat count parameter that defaults to looping forever.
  • The distutils sdist command now ignores all .svn directories, in addition to CVS and RCS directories. .svn directories hold administrative files for the Subversion source control system.
  • Added a new module: cookielib. Automatic cookie handling for HTTP clients. Also, support for cookielib has been added to urllib2, so urllib2.urlopen() can transparently handle cookies.
  • now uses built-in set() instead of sets.Set().
  • Bug #876278: Unbounded recursion in modulefinder
  • Bug #780300: Swap public and system ID in LexicalHandler.startDTD. Applications relying on the wrong order need to be corrected.
  • Bug #926075: Fixed a bug that returns a wrong pattern object for a string or unicode object in sre.compile() when a different type pattern with the same value exists.
  • Added countcallers arg to trace.Trace class (--trackcalls command line arg when run from the command prompt).
  • Fixed a caching bug in platform.platform() where the argument of 'terse' was not taken into consideration when caching value.
  • Added two new command-line arguments for profile (output file and default sort).
  • Added global runctx function to profile module
  • Add hlist missing entryconfigure and entrycget methods.
  • The ptcp154 codec was added for Kazakh character set support.
  • Support non-anonymous ftp URLs in urllib2.
  • The encodings package will now apply codec name aliases first before starting to try the import of the codec module. This simplifies overriding built-in codecs with external packages, e.g. the included CJK codecs with the JapaneseCodecs package, by adjusting the aliases dictionary in encodings.aliases accordingly.
  • base64 now supports RFC 3548 Base16, Base32, and Base64 encoding and decoding standards.
  • urllib2 now supports processors. A processor is a handler that implements an xxx_request or xxx_response method. These methods are called for all requests.
  • distutils compilers now compile source files in the same order as they are passed to the compiler.
  • pprint.pprint() and pprint.pformat() now have additional parameters indent, width and depth.
  • Patch #750542: pprint now will pretty print subclasses of list, tuple and dict too, as long as they don't overwrite __repr__().
  • Bug #848614: distutils' msvccompiler fails to find the MSVC6 compiler because of incomplete registry entries.
  • httplib.HTTP.putrequest now offers to omit the implicit Accept-Encoding.
  • Patch #841977: modulefinder didn't find extension modules in packages
  • imaplib.IMAP4.thread was added.
  • Plugged a minor hole in tempfile.mktemp() due to the use of os.path.exists(), switched to using os.lstat() directly if possible.
  • and now have underlying C implementations for better performance.
  • has two new functions, nsmallest() and nlargest().
  • traceback.format_exc has been added (similar to print_exc but it returns a string).
  • xmlrpclib.MultiCall has been added.
  • poplib.POP3_SSL has been added.
  • tmpfile.mkstemp now returns an absolute path even if dir is relative.
  • urlparse is RFC 2396 compliant.
  • The fieldnames argument to the csv module's DictReader constructor is now optional. If omitted, the first row of the file will be used as the list of fieldnames.
  • encodings.bz2_codec was added for access to bz2 compression using "a long string".encode('bz2')
  • Various improvements to, realigned with PyUnit CVS.
  • dircache now passes exceptions to the caller, instead of returning empty lists.
  • The bsddb module and dbhash module now support the iterator and mapping protocols which make them more substitutable for dictionaries and shelves.
  • The csv module's DictReader and DictWriter classes now accept keyword arguments. This was an omission in the initial implementation.
  • The email package handles some RFC 2231 parameters with missing CHARSET fields better. It also includes a patch to parameter parsing when semicolons appear inside quotes.
  • now runs under Py2.2. In addition, the argument restrictions for most set methods (but not the operators) have been relaxed to allow any iterable.
  • now has a behind-the-scenes caching mechanism for the most recent TimeRE instance used along with the last five unique directive patterns. The overall module was also made more thread-safe.
  • random.cunifvariate() and random.stdgamma() were deprecated in Py2.3 and removed in Py2.4.
  • Bug #823328:'s HTTP Digest Auth support works again.
  • Patch #873597: CJK codecs are imported into rank of default codecs.


  • A hotshotmain script was added to the Tools/scripts directory that makes it easy to run a script under control of the hotshot profiler.
  • The db2pickle and pickle2db scripts can now dump/load gdbm files.
  • The file order on the command line of the pickle2db script was reversed. It is now [ picklefile ] dbfile. This provides better symmetry with db2pickle. The file arguments to both scripts are now source followed by destination in situations where both files are given.
  • The pydoc script will display a link to the module documentation for modules determined to be part of the core distribution. The documentation base directory defaults to but can be changed by setting the PYTHONDOCS environment variable.
  • now detects double word errors.
  • mistakenly opened input files in text mode by default, a silent and dangerous change from previous releases. It once again opens input files in binary mode by default. The -t and -b flags remain for compatibility with the 2.3 release, but -b is the default now.
  • py-electric-colon now works when pending-delete/delete-selection mode is in effect
  • py-help-at-point is no longer bound to the F1 key - it's still bound to C-c C-h
  • Pynche was fixed to not crash when there is no ~/.pynche file and no -d option was given.


  • Bug #978645: Modules/getpath.c now builds properly in --disable-framework build under OS X.
  • Profiling using gprof is now available if Python is configured with --enable-profiling.
  • Profiling the VM using the Pentium TSC is now possible if Python is configured --with-tsc.
  • In order to find libraries, now also looks in /lib64, for use on AMD64.
  • Bug #934635: Fixed a bug where the configure script couldn't detect getaddrinfo() properly if the KAME stack had SCTP support.
  • Support for missing ANSI C header files (limits.h, stddef.h, etc) was removed.
  • Systems requiring the D4, D6 or D7 variants of pthreads are no longer supported (see PEP 11).
  • Universal newline support can no longer be disabled (see PEP 11).
  • Support for DGUX, SunOS 4, IRIX 4 and Minix was removed (see PEP 11).
  • Support for systems requiring --with-dl-dld or --with-sgi-dl was removed (see PEP 11).
  • Tests for sizeof(char) were removed since ANSI C mandates that sizeof(char) must be 1.


  • Thanks to Anthony Tuininga, the datetime module now supplies a C API containing type-check macros and constructors. See new docs in the Python/C API Reference Manual for details.
  • Private function _PyTime_DoubleToTimet added, to convert a Python timestamp (C double) to platform time_t with some out-of-bounds checking. Declared in new header file timefuncs.h. It would be good to expose some other internal timemodule.c functions there.
  • New public functions PyEval_EvaluateFrame and PyGen_New to expose generator objects.
  • New public functions Py_IncRef() and Py_DecRef(), exposing the functionality of the Py_XINCREF() and Py_XDECREF macros. Useful for runtime dynamic embedding of Python. See patch #938302, by Bob Ippolito.
  • Added a new macro, PySequence_Fast_ITEMS, which retrieves a fast sequence's underlying array of PyObject pointers. Useful for high speed looping.
  • Created a new method flag, METH_COEXIST, which causes a method to be loaded even if already defined by a slot wrapper. This allows a __contains__ method, for example, to co-exist with a defined sq_contains slot. This is helpful because the PyCFunction can take advantage of optimized calls whenever METH_O or METH_NOARGS flags are defined.
  • Added a new function, PyDict_Contains(d, k) which is like PySequence_Contains() but is specific to dictionaries and executes about 10% faster.
  • Added three new macros: Py_RETURN_NONE, Py_RETURN_TRUE, and Py_RETURN_FALSE. Each return the singleton they mention after Py_INCREF()ing them.
  • Added a new function, PyTuple_Pack(n, ...) for constructing tuples from a variable length argument list of Python objects without having to invoke the more complex machinery of Py_BuildValue(). PyTuple_Pack(3, a, b, c) is equivalent to Py_BuildValue("(OOO)", a, b, c).


  • The _winreg module could segfault when reading very large registry values, due to unchecked alloca() calls (SF bug 851056). The fix is uses either PyMem_Malloc(n) or PyString_FromStringAndSize(NULL, n), as appropriate, followed by a size check.
  • file.truncate() could misbehave if the file was open for update (modes r+, rb+, w+, wb+), and the most recent file operation before the truncate() call was an input operation. SF bug 801631.

What's New in Python 2.3 final?

Release date: 29-Jul-2003


  • Bug 778400: IDLE hangs when selecting "Edit with IDLE" from explorer. This was unique to Windows, and was fixed by adding an -n switch to the command the Windows installer creates to execute "Edit with IDLE" context-menu actions.
  • IDLE displays a new message upon startup: some "personal firewall" kinds of programs (for example, ZoneAlarm) open a dialog of their own when any program opens a socket. IDLE does use sockets, talking on the computer's internal loopback interface. This connection is not visible on any external interface and no data is sent to or received from the Internet. So, if you get such a dialog when opening IDLE, asking whether to let pythonw.exe talk to address, say yes, and rest assured no communication external to your machine is taking place. If you don't allow it, IDLE won't be able to start.

What's New in Python 2.3 release candidate 2?

Release date: 24-Jul-2003

Core and builtins

  • It is now possible to import from zipfiles containing additional data bytes before the zip compatible archive. Zipfiles containing a comment at the end are still unsupported.

Extension modules

  • A longstanding bug in the parser module's initialization could cause fatal internal refcount confusion when the module got initialized more than once. This has been fixed.
  • Fixed memory leak in pyexpat; using the parser's ParseFile() method with open files that aren't instances of the standard file type caused an instance of the bound .read() method to be leaked on every call.
  • Fixed some leaks in the locale module.


  • Lib/encodings/ when used as a script, now more properly uses the first Python interpreter on your path.
  • Removed caching of TimeRE (and thus LocaleTime) in to fix a locale related bug in the test suite. Although another patch was needed to actually fix the problem, the cache code was not restored.


  • Calltips patches.


  • For MacOSX, added -mno-fused-madd to BASECFLAGS to fix test_coercion on Panther (OSX 10.3).



  • The tempfile module could do insane imports on Windows if PYTHONCASEOK was set, making temp file creation impossible. Repaired.
  • Add a patch to workaround pthread_sigmask() bugs in Cygwin.


  • Various fixes to pimp.
  • Scripts runs with pythonw no longer had full window manager access.
  • Don't force boot-disk-only install, for reasons unknown it causes more problems than it solves.

What's New in Python 2.3 release candidate 1?

Release date: 18-Jul-2003

Core and builtins

  • The new function sys.getcheckinterval() returns the last value set by sys.setcheckinterval().
  • Several bugs in the symbol table phase of the compiler have been fixed. Errors could be lost and compilation could fail without reporting an error. SF patch 763201.
  • The interpreter is now more robust about importing the warnings module. In an executable generated by freeze or similar programs, earlier versions of 2.3 would fail if the warnings module could not be found on the file system. Fixes SF bug 771097.
  • A warning about assignments to module attributes that shadow builtins, present in earlier releases of 2.3, has been removed.
  • It is not possible to create subclasses of builtin types like str and tuple that define an itemsize. Earlier releases of Python 2.3 allowed this by mistake, leading to crashes and other problems.
  • The thread_id is now initialized to 0 in a non-thread build. SF bug 770247.
  • SF bug 762891: "del p[key]" on proxy object no longer raises SystemError.

Extension modules

  • weakref.proxy() can now handle "del obj[i]" for proxy objects defining __delitem__. Formerly, it generated a SystemError.

  • SSL no longer crashes the interpreter when the remote side disconnects.

  • On Unix the mmap module can again be used to map device files.

  • time.strptime now exclusively uses the Python implementation contained within the _strptime module.

  • The print slot of weakref proxy objects was removed, because it was not consistent with the object's repr slot.

  • The mmap module only checks file size for regular files, not character or block devices. SF patch 708374.

  • The cPickle Pickler garbage collection support was fixed to traverse the find_class attribute, if present.

  • There are several fixes for the bsddb3 wrapper module.

    bsddb3 no longer crashes if an environment is closed before a cursor (SF bug 763298).

    The DB and DBEnv set_get_returns_none function was extended to take a level instead of a boolean flag. The new level 2 means that in addition, cursor.set()/.get() methods return None instead of raising an exception.

    A typo was fixed in DBCursor.join_item(), preventing a crash.


  • distutils now supports MSVC 7.1

  • doctest now examines all docstrings by default. Previously, it would skip over functions with private names (as indicated by the underscore naming convention). The old default created too much of a risk that user tests were being skipped inadvertently. Note, this change could break code in the unlikely case that someone had intentionally put failing tests in the docstrings of private functions. The breakage is easily fixable by specifying the old behavior when calling testmod() or Tester().

  • There were several fixes to the way dumbdbms are closed. It's vital that a dumbdbm database be closed properly, else the on-disk data and directory files can be left in mutually inconsistent states.'s _Database.__del__() method attempted to close the database properly, but a shutdown race in _Database._commit() could prevent this from working, so that a program trusting __del__() to get the on-disk files in synch could be badly surprised. The race has been repaired. A sync() method was also added so that shelve can guarantee data is written to disk.

    The close() method can now be called more than once without complaint.

  • The classes in are now new-style classes. That they weren't before was an oversight.

  • The urllib2 digest authentication handlers now define the correct auth_header. The earlier versions would fail at runtime.

  • SF bug 763023: fix uncaught ZeroDivisionError in difflib ratio methods when there are no lines.

  • SF bug 763637: fix exception in Tkinter with after_cancel which could occur with Tk 8.4

  • SF bug 770601: now passes the entire environment to child processes.

  • SF bug 765238: add filter to fnmatch's __all__.

  • SF bug 748201: make time.strptime() error messages more helpful.

  • SF patch 764470: Do not dump the args attribute of a Fault object in xmlrpclib.

  • SF patch 549151: urllib and urllib2 now redirect POSTs on 301 responses.

  • SF patch 766650: The whichdb module was fixed to recognize dbm files generated by gdbm on OS/2 EMX.

  • SF bugs 763047 and 763052: fixes bug of timezone value being left as -1 when time.tzname[0] == time.tzname[1] and not time.daylight is true when it should only when time.daylight is true.

  • SF bug 764548: re now allows subclasses of str and unicode to be used as patterns.

  • SF bug 763637: In Tkinter, change after_cancel() to handle tuples of varying sizes. Tk 8.4 returns a different number of values than Tk 8.3.

  • SF bug 763023: difflib.ratio() did not catch zero division.

  • The Queue module now has an __all__ attribute.


  • See Lib/idlelib/NEWS.txt for IDLE news.
  • SF bug 753592: webchecker/wsgui now handles user supplied directories.
  • The script has been removed. It is now in the standard library.


  • Python now compiles with -fno-strict-aliasing if possible (SF bug 766696).
  • The socket module compiles on IRIX 6.5.10.
  • An irix64 system is treated the same way as an irix6 system (SF patch 764560).
  • Several definitions were missing on FreeBSD 5.x unless the __BSD_VISIBLE symbol was defined. configure now defines it as needed.


  • Unicode objects now support mbcs as a built-in encoding, so the C API can use it without deferring to the encodings package.


  • The Windows implementation of PyThread_start_new_thread() never checked error returns from Windows functions correctly. As a result, it could claim to start a new thread even when the Microsoft _beginthread() function failed (due to "too many threads" -- this is on the order of thousands when it happens). In these cases, the Python exception

    thread.error: can't start new thread

    is raised now.

  • SF bug 766669: Prevent a GPF on interpreter exit when sockets are in use. The interpreter now calls WSACleanup() from Py_Finalize() instead of from DLL teardown.


  • Bundlebuilder now inherits default values in the right way. It was previously possible for app bundles to get a type of "BNDL" instead of "APPL." Other improvements include, a --build-id option to specify the CFBundleIdentifier and using the --python option to set the executable in the bundle.
  • Fixed two bugs in MacOSX framework handling.
  • pythonw did not allow user interaction in 2.3rc1, this has been fixed.
  • Python is now compiled with -mno-fused-madd, making all tests pass on Panther.

What's New in Python 2.3 beta 2?

Release date: 29-Jun-2003

Core and builtins

  • A program can now set the environment variable PYTHONINSPECT to some string value in Python, and cause the interpreter to enter the interactive prompt at program exit, as if Python had been invoked with the -i option.
  • list.index() now accepts optional start and stop arguments. Similar changes were made to UserList.index(). SF feature request 754014.
  • SF patch 751998 fixes an unwanted side effect of the previous fix for SF bug 742860 (the next item).
  • SF bug 742860: "WeakKeyDictionary __delitem__ uses iterkeys". This wasn't threadsafe, was very inefficient (expected time O(len(dict)) instead of O(1)), and could raise a spurious RuntimeError if another thread mutated the dict during __delitem__, or if a comparison function mutated it. It also neglected to raise KeyError when the key wasn't present; didn't raise TypeError when the key wasn't of a type which could be weakly referenced; and broke various more-or-less obscure dict invariants by using a sequence of equality comparisons over the whole set of dict keys instead of computing the key's hash code to narrow the search to those keys with the same hash code. All of these are considered to be bugs. A new implementation of __delitem__ repairs all that, but note that fixing these bugs may change visible behavior in code relying (whether intentionally or accidentally) on old behavior.
  • SF bug 734869: Fixed a compiler bug that caused a fatal error when compiling a list comprehension that contained another list comprehension embedded in a lambda expression.
  • SF bug 705231: builtin pow() no longer lets the platform C pow() raise -1.0 to integer powers, because (at least) glibc gets it wrong in some cases. The result should be -1.0 if the power is odd and 1.0 if the power is even, and any float with a sufficiently large exponent is (mathematically) an exact even integer.
  • SF bug 759227: A new-style class that implements __nonzero__() must return a bool or int (but not an int subclass) from that method. This matches the restriction on classic classes.
  • The encoding attribute has been added for file objects, and set to the terminal encoding on Unix and Windows.
  • The softspace attribute of file objects became read-only by oversight. It's writable again.
  • Reverted a 2.3 beta 1 change to iterators for subclasses of list and tuple. By default, the iterators now access data elements directly instead of going through __getitem__. If __getitem__ access is preferred, then __iter__ can be overridden.
  • SF bug 735247: The staticmethod and super types participate in garbage collection. Before this change, it was possible for leaks to occur in functions with non-global free variables that used these types.

Extension modules

  • the socket module has a new exception, socket.timeout, to allow timeouts to be handled separately from other socket errors.
  • SF bug 751276: cPickle has fixed to propagate exceptions raised in user code. In earlier versions, cPickle caught and ignored any exception when it performed operations that it expected to raise specific exceptions like AttributeError.
  • cPickle Pickler and Unpickler objects now participate in garbage collection.
  • mimetools.choose_boundary() could return duplicate strings at times, especially likely on Windows. The strings returned are now guaranteed unique within a single program run.
  • thread.interrupt_main() raises KeyboardInterrupt in the main thread. dummy_thread has also been modified to try to simulate the behavior.
  • array.array.insert() now treats negative indices as being relative to the end of the array, just like list.insert() does. (SF bug #739313)
  • The datetime module classes datetime, time, and timedelta are now properly subclassable.
  • _tkinter.{get|set}busywaitinterval was added.
  • itertools.islice() now accepts stop=None as documented. Fixes SF bug #730685.
  • the bsddb185 module is built in one restricted instance - /usr/include/db.h exists and defines HASHVERSION to be 2. This is true for many BSD-derived systems.


  • Some happy doctest extensions from Jim Fulton have been added to These are already being used in Zope3. The two primary ones:

    doctest.debug(module, name) extracts the doctests from the named object in the given module, puts them in a temp file, and starts pdb running on that file. This is great when a doctest fails.

    doctest.DocTestSuite(module=None) returns a synthesized unittest TestSuite instance, to be run by the unittest framework, which runs all the doctests in the module. This allows writing tests in doctest style (which can be clearer and shorter than writing tests in unittest style), without losing unittest's powerful testing framework features (which doctest lacks).

  • For compatibility with doctests created before 2.3, if an expected output block consists solely of "1" and the actual output block consists solely of "True", it's accepted as a match; similarly for "0" and "False". This is quite un-doctest-like, but is practical. The behavior can be disabled by passing the new doctest module constant DONT_ACCEPT_TRUE_FOR_1 to the new optionflags optional argument.

  • ZipFile.testzip() now only traps BadZipfile exceptions. Previously, a bare except caught to much and reported all errors as a problem in the archive.

  • The logging module now has a new function, makeLogRecord() making LogHandler easier to interact with DatagramHandler and SocketHandler.

  • The cgitb module has been extended to support plain text display (SF patch 569574).

  • A brand new version of IDLE (from the IDLEfork project at SourceForge) is now included as Lib/idlelib. The old Tools/idle is no more.

  • Added a new module: trace (documentation missing). This module used to be distributed in Tools/scripts. It uses sys.settrace() to trace code execution -- either function calls or individual lines. It can generate tracing output during execution or a post-mortem report of code coverage.

  • The threading module has new functions settrace() and setprofile() that cooperate with the functions of the same name in the sys module. A function registered with the threading module will be used for all threads it creates. The new trace module uses this to provide tracing for code running in threads.

  • applied SF patch 707900, fixing bug 702858, by Steven Taschuk. Copying a new-style class that had a reference to itself didn't work. (The same thing worked fine for old-style classes.) Builtin functions are now treated as atomic, fixing bug #746304.

  • has two new functions: context_diff() and unified_diff().

  • More fixes to urllib (SF 549151): (a) When redirecting, always use GET. This is common practice and more-or-less sanctioned by the HTTP standard. (b) Add a handler for 307 redirection, which becomes an error for POST, but a regular redirect for GET and HEAD

  • Added optional 'onerror' argument to os.walk(), to control error handling.

  •{method|data}descriptor was added, to allow pydoc display __doc__ of data descriptors.

  • Fixed socket speed loss caused by use of the _socketobject wrapper class in

  • now checks the current directory for imports.

  • now knows how to order proxy classes, so the user doesn't have to insert it in front of other classes, nor do dirty tricks like inserting a "dummy" HTTPHandler after a ProxyHandler when building an opener with proxy support.

  • Iterators have been added for dbm keys.

  • random.Random objects can now be pickled.


  • pydoc now offers help on keywords and topics.
  • Tools/idle is gone; long live Lib/idlelib.
  • prints file diffs in context, unified, or ndiff formats, providing a command line interface to
  • is a new script for making a rough validation of Python LaTeX files.


  • Setting DESTDIR during 'make install' now allows specifying a different root directory.


  • PyType_Ready(): If a type declares that it participates in gc (Py_TPFLAGS_HAVE_GC), and its base class does not, and its base class's tp_free slot is the default _PyObject_Del, and type does not define a tp_free slot itself, _PyObject_GC_Del is assigned to type->tp_free. Previously _PyObject_Del was inherited, which could at best lead to a segfault. In addition, if even after this magic the type's tp_free slot is _PyObject_Del or NULL, and the type is a base type (Py_TPFLAGS_BASETYPE), TypeError is raised: since the type is a base type, its dealloc function must call type->tp_free, and since the type is gc'able, tp_free must not be NULL or _PyObject_Del.
  • PyThreadState_SetAsyncExc(): A new API (deliberately accessible only from C) to interrupt a thread by sending it an exception. It is intentional that you have to write your own C extension to call it from Python.

New platforms

None this time.


  • test_imp rewritten so that it doesn't raise RuntimeError if run as a side effect of being imported ("import test.autotest").


  • The Windows installer ships with Tcl/Tk 8.4.3 (upgraded from 8.4.1).
  • The installer always suggested that Python be installed on the C: drive, due to a hardcoded "C:" generated by the Wise installation wizard. People with machines where C: is not the system drive usually want Python installed on whichever drive is their system drive instead. We removed the hardcoded "C:", and two testers on machines where C: is not the system drive report that the installer now suggests their system drive. Note that you can always select the directory you want in the "Select Destination Directory" dialog -- that's what it's for.


  • There's a new module called "autoGIL", which offers a mechanism to automatically release the Global Interpreter Lock when an event loop goes to sleep, allowing other threads to run. It's currently only supported on OSX, in the Mach-O version.
  • The OSA modules now allow direct access to properties of the toplevel application class (in AppleScript terminology).
  • The Package Manager can now update itself.

SourceForge Bugs and Patches Applied

430160, 471893, 501716, 542562, 549151, 569574, 595837, 596434, 598163, 604210, 604716, 610332, 612627, 614770, 620190, 621891, 622042, 639139, 640236, 644345, 649742, 649742, 658233, 660022, 661318, 661676, 662807, 662923, 666219, 672855, 678325, 682347, 683486, 684981, 685773, 686254, 692776, 692959, 693094, 696777, 697989, 700827, 703666, 708495, 708604, 708901, 710733, 711902, 713722, 715782, 718286, 719359, 719367, 723136, 723831, 723962, 724588, 724767, 724767, 725942, 726150, 726446, 726869, 727051, 727719, 727719, 727805, 728277, 728563, 728656, 729096, 729103, 729293, 729297, 729300, 729317, 729395, 729622, 729817, 730170, 730296, 730594, 730685, 730826, 730963, 731209, 731403, 731504, 731514, 731626, 731635, 731643, 731644, 731644, 731689, 732124, 732143, 732234, 732284, 732284, 732479, 732761, 732783, 732951, 733667, 733781, 734118, 734231, 734869, 735051, 735293, 735527, 735613, 735694, 736962, 736962, 737970, 738066, 739313, 740055, 740234, 740301, 741806, 742126, 742741, 742860, 742860, 742911, 744041, 744104, 744238, 744687, 744877, 745055, 745478, 745525, 745620, 746012, 746304, 746366, 746801, 746953, 747348, 747667, 747954, 748846, 748849, 748973, 748975, 749191, 749210, 749759, 749831, 749911, 750008, 750092, 750542, 750595, 751038, 751107, 751276, 751451, 751916, 751941, 751956, 751998, 752671, 753451, 753602, 753617, 753845, 753925, 754014, 754340, 754447, 755031, 755087, 755147, 755245, 755683, 755987, 756032, 756996, 757058, 757229, 757818, 757821, 757822, 758112, 758910, 759227, 759889, 760257, 760703, 760792, 761104, 761337, 761519, 761830, 762455

What's New in Python 2.3 beta 1?

Release date: 25-Apr-2003

Core and builtins

  • New format codes B, H, I, k and K have been implemented for PyArg_ParseTuple and PyBuild_Value.
  • New builtin function sum(seq, start=0) returns the sum of all the items in iterable object seq, plus start (items are normally numbers, and cannot be strings).
  • bool() called without arguments now returns False rather than raising an exception. This is consistent with calling the constructors for the other builtin types -- called without argument they all return the false value of that type. (SF patch #724135)
  • In support of PEP 269 (making the pgen parser generator accessible from Python), some changes to the pgen code structure were made; a few files that used to be linked only with pgen are now linked with Python itself.
  • The repr() of a weakref object now shows the __name__ attribute of the referenced object, if it has one.
  • super() no longer ignores data descriptors, except __class__. See the thread started at
  • list.insert(i, x) now interprets negative i as it would be interpreted by slicing, so negative values count from the end of the list. This was the only place where such an interpretation was not placed on a list index.
  • range() now works even if the arguments are longs with magnitude larger than sys.maxint, as long as the total length of the sequence fits. E.g., range(2**100, 2**101, 2**100) is the following list: [1267650600228229401496703205376L]. (SF patch #707427.)
  • Some horridly obscure problems were fixed involving interaction between garbage collection and old-style classes with "ambitious" getattr hooks. If an old-style instance didn't have a __del__ method, but did have a __getattr__ hook, and the instance became reachable only from an unreachable cycle, and the hook resurrected or deleted unreachable objects when asked to resolve "__del__", anything up to a segfault could happen. That's been repaired.
  • dict.pop now takes an optional argument specifying a default value to return if the key is not in the dict. If a default is not given and the key is not found, a KeyError will still be raised. Parallel changes were made to UserDict.UserDict and UserDict.DictMixin. [SF patch #693753] (contributed by Michael Stone.)
  • sys.getfilesystemencoding() was added to expose Py_FileSystemDefaultEncoding.
  • New function sys.exc_clear() clears the current exception. This is rarely needed, but can sometimes be useful to release objects referenced by the traceback held in sys.exc_info()[2]. (SF patch #693195.)
  • On 64-bit systems, a dictionary could contain duplicate long/int keys if the key value was larger than 2**32. See SF bug #689659.
  • Fixed SF bug #663074. The codec system was using global static variables to store internal data. As a result, any attempts to use the unicode system with multiple active interpreters, or successive interpreter executions, would fail.
  • "%c" % u"a" now returns a unicode string instead of raising a TypeError. u"%c" % 0xffffffff now raises a OverflowError instead of a ValueError to be consistent with "%c" % 256. See SF patch #710127.

Extension modules

  • The socket module now provides the functions inet_pton and inet_ntop for converting between string and packed representation of IP addresses. There is also a new module variable, has_ipv6, which is True iff the current Python has IPv6 support. See SF patch #658327.
  • Tkinter wrappers around Tcl variables now pass objects directly to Tcl, instead of first converting them to strings.
  • The .*? pattern in the re module is now special-cased to avoid the recursion limit. (SF patch #720991 -- many thanks to Gary Herron and Greg Chapman.)
  • New function sys.call_tracing() allows pdb to debug code recursively.
  • New function gc.get_referents(obj) returns a list of objects directly referenced by obj. In effect, it exposes what the object's tp_traverse slot does, and can be helpful when debugging memory leaks.
  • The iconv module has been removed from this release.
  • The platform-independent routines for packing floats in IEEE formats (struct.pack's <f, >f, <d, and >d codes; pickle and cPickle's protocol 1 pickling of floats) ignored that rounding can cause a carry to propagate. The worst consequence was that, in rare cases, <f and >f could produce strings that, when unpacked again, were a factor of 2 away from the original float. This has been fixed. See SF bug #705836.
  • New function time.tzset() provides access to the C library tzset() function, if supported. (SF patch #675422.)
  • Using createfilehandler, deletefilehandler, createtimerhandler functions on Tkinter.tkinter (_tkinter module) no longer crashes the interpreter. See SF bug #692416.
  • Modified the fcntl.ioctl() function to allow modification of a passed mutable buffer (for details see the reference documentation).
  • Made user requested changes to the itertools module. Subsumed the times() function into repeat(). Added chain() and cycle().
  • The rotor module is now deprecated; the encryption algorithm it uses is not believed to be secure, and including crypto code with Python has implications for exporting and importing it in various countries.
  • The socket module now always uses the _socketobject wrapper class, even on platforms which have dup(2). The makefile() method is built directly on top of the socket without duplicating the file descriptor, allowing timeouts to work properly.


  • New generator function os.walk() is an easy-to-use alternative to os.path.walk(). See os module docs for details. os.path.walk() isn't deprecated at this time, but may become deprecated in a future release.
  • Added new module "platform" which provides a wide range of tools for querying platform dependent features.
  • netrc now allows ASCII punctuation characters in passwords.
  • shelve now supports the optional writeback argument, and exposes pickle protocol versions.
  • Several methods of nntplib.NNTP have grown an optional file argument which specifies a file where to divert the command's output (already supported by the body() method). (SF patch #720468)
  • The self-documenting XML server library DocXMLRPCServer was added.
  • Support for internationalized domain names has been added through the 'idna' and 'punycode' encodings, the 'stringprep' module, the 'mkstringprep' tool, and enhancements to the socket and httplib modules.
  • htmlentitydefs has two new dictionaries: name2codepoint maps HTML entity names to Unicode codepoints (as integers). codepoint2name is the reverse mapping. See SF patch #722017.
  • pdb has a new command, "debug", which lets you step through arbitrary code from the debugger's (pdb) prompt.
  • unittest.failUnlessEqual and its equivalent unittest.assertEqual now return 'not a == b' rather than 'a != b'. This gives the desired result for classes that define __eq__ without defining __ne__.
  • sgmllib now supports SGML marked sections, in particular the MS Office extensions.
  • The urllib module now offers support for the iterator protocol. SF patch 698520 contributed by Brett Cannon.
  • New module timeit provides a simple framework for timing the execution speed of expressions and statements.
  • sets.Set objects now support mixed-type __eq__ and __ne__, instead of raising TypeError. If x is a Set object and y is a non-Set object, x == y is False, and x != y is True. This is akin to the change made for mixed-type comparisons of datetime objects in 2.3a2; more info about the rationale is in the NEWS entry for that. See also SF bug report <>.
  • On Unix platforms, if os.listdir() is called with a Unicode argument, it now returns Unicode strings. (This behavior was added earlier to the Windows NT/2k/XP version of os.listdir().)
  • Distutils: both 'py_modules' and 'packages' keywords can now be specified in core.setup(). Previously you could supply one or the other, but not both of them. (SF patch #695090 from Bernhard Herzog)
  • New csv package makes it easy to read/write CSV files.
  • Module shlex has been extended to allow posix-like shell parsings, including a split() function for easy splitting of quoted strings and commands. An iterator interface was also implemented.


  • New script helps analyze new PYTHONDUMPREFS output. See the module docstring for details.


  • Fix problem building on OSF1 because the compiler only accepted preprocessor directives that start in column 1. (SF bug #691793.)


  • Added PyGC_Collect(), equivalent to calling gc.collect().

  • PyThreadState_GetDict() was changed not to raise an exception or issue a fatal error when no current thread state is available. This makes it possible to print dictionaries when no thread is active.

  • LONG_LONG was renamed to PY_LONG_LONG. Extensions that use this and need compatibility with previous versions can use this:

    #ifndef PY_LONG_LONG #define PY_LONG_LONG LONG_LONG #endif

  • Added PyObject_SelfIter() to fill the tp_iter slot for the typical case where the method returns its self argument.

  • The extended type structure used for heap types (new-style classes defined by Python code using a class statement) is now exported from object.h as PyHeapTypeObject. (SF patch #696193.)

New platforms

None this time.


  • test_timeout now requires -u network to be passed to regrtest to run. See SF bug #692988.


  • os.fsync() now exists on Windows, and calls the Microsoft _commit() function.
  • New function winsound.MessageBeep() wraps the Win32 API MessageBeep().


  • os.listdir() now returns Unicode strings on MacOS X when called with a Unicode argument. See the general news item under "Library".
  • A new method MacOS.WMAvailable() returns true if it is safe to access the window manager, false otherwise.
  • EasyDialogs dialogs are now movable-modal, and if the application is currently in the background they will ask to be moved to the foreground before displaying.
  • OSA Scripting support has improved a lot, and can now be used by mere mortals. The documentation is now also more or less complete.
  • The IDE (in a framework build) now includes introductory documentation in Apple Help Viewer format.

What's New in Python 2.3 alpha 2?

Release date: 19-Feb-2003

Core and builtins

  • Negative positions returned from PEP 293 error callbacks are now treated as being relative to the end of the input string. Positions that are out of bounds raise an IndexError.
  • sys.path[0] (the directory from which the script is loaded) is now turned into an absolute pathname, unless it is the empty string. (SF patch #664376.)
  • Finally fixed the bug in compile() and exec where a string ending with an indented code block but no newline would raise SyntaxError. This would have been a four-line change in parsetok.c... Except depends on this behavior, so a compilation flag had to be invented that causes the tokenizer to revert to the old behavior; this required extra changes to 2 .h files, 2 .c files, and 2 .py files. (Fixes SF bug #501622.)
  • If a new-style class defines neither __new__ nor __init__, its constructor would ignore all arguments. This is changed now: the constructor refuses arguments in this case. This might break code that worked under Python 2.2. The simplest fix is to add a no-op __init__: def __init__(self, *args, **kw): pass.
  • Through a bytecode optimizer bug (and I bet you didn't even know Python had a bytecode optimizer :-), "unsigned" hex/oct constants with a leading minus sign would come out with the wrong sign. ("Unsigned" hex/oct constants are those with a face value in the range sys.maxint+1 through sys.maxint*2+1, inclusive; these have always been interpreted as negative numbers through sign folding.) E.g. 0xffffffff is -1, and -(0xffffffff) is 1, but -0xffffffff would come out as -4294967295. This was the case in Python 2.2 through 2.2.2 and 2.3a1, and in Python 2.4 it will once again have that value, but according to PEP 237 it really needs to be 1 now. This will be backported to Python 2.2.3 a well. (SF #660455)
  • int(s, base) sometimes sign-folds hex and oct constants; it only does this when base is 0 and s.strip() starts with a '0'. When the sign is actually folded, as in int("0xffffffff", 0) on a 32-bit machine, which returns -1, a FutureWarning is now issued; in Python 2.4, this will return 4294967295L, as do int("+0xffffffff", 0) and int("0xffffffff", 16) right now. (PEP 347)
  • super(X, x): x may now be a proxy for an X instance, i.e. issubclass(x.__class__, X) but not issubclass(type(x), X).
  • isinstance(x, X): if X is a new-style class, this is now equivalent to issubclass(type(x), X) or issubclass(x.__class__, X). Previously only type(x) was tested. (For classic classes this was already the case.)
  • compile(), eval() and the exec statement now fully support source code passed as unicode strings.
  • int subclasses can be initialized with longs if the value fits in an int. See SF bug #683467.
  • long(string, base) takes time linear in len(string) when base is a power of 2 now. It used to take time quadratic in len(string).
  • filter returns now Unicode results for Unicode arguments.
  • raw_input can now return Unicode objects.
  • List objects' sort() method now accepts None as the comparison function. Passing None is semantically identical to calling sort() with no arguments.
  • Fixed crash when printing a subclass of str and __str__ returned self. See SF bug #667147.
  • Fixed an invalid RuntimeWarning and an undetected error when trying to convert a long integer into a float which couldn't fit. See SF bug #676155.
  • Function objects now have a __module__ attribute that is bound to the name of the module in which the function was defined. This applies for C functions and methods as well as functions and methods defined in Python. This attribute is used by pickle.whichmodule(), which changes the behavior of whichmodule slightly. In Python 2.2 whichmodule() returns "__main__" for functions that are not defined at the top-level of a module (examples: methods, nested functions). Now whichmodule() will return the proper module name.

Extension modules

  • operator.isNumberType() now checks that the object has a nb_int or nb_float slot, rather than simply checking whether it has a non-NULL tp_as_number pointer.

  • The imp module now has ways to acquire and release the "import lock": imp.acquire_lock() and imp.release_lock(). Note: this is a reentrant lock, so releasing the lock only truly releases it when this is the last release_lock() call. You can check with imp.lock_held(). (SF bug #580952 and patch #683257.)

  • Change to cPickle to match (see below and PEP 307).

  • Fix some bugs in the parser module. SF bug #678518.

  • Thanks to Scott David Daniels, a subtle bug in how the zlib extension implemented flush() was fixed. Scott also rewrote the zlib test suite using the unittest module. (SF bug #640230 and patch #678531.)

  • Added an itertools module containing high speed, memory efficient looping constructs inspired by tools from Haskell and SML.

  • The SSL module now handles sockets with a timeout set correctly (SF patch #675750, fixing SF bug #675552).

  • os/posixmodule has grown the sysexits.h constants (EX_OK and friends).

  • Fixed broken threadstate swap in readline that could cause fatal errors when a readline hook was being invoked while a background thread was active. (SF bugs #660476 and #513033.)

  • fcntl now exposes the strops.h I_* constants.

  • Fix a crash on Solaris that occurred when calling close() on an mmap'ed file which was already closed. (SF patch #665913)

  • Fixed several serious bugs in the zipimport implementation.

  • datetime changes:

    The date class is now properly subclassable. (SF bug #720908)

    The datetime and datetimetz classes have been collapsed into a single datetime class, and likewise the time and timetz classes into a single time class. Previously, a datetimetz object with tzinfo=None acted exactly like a datetime object, and similarly for timetz. This wasn't enough of a difference to justify distinct classes, and life is simpler now.

    today() and now() now round system timestamps to the closest microsecond <>. This repairs an irritation most likely seen on Windows systems.

    In dt.astimezone(tz), if tz.utcoffset(dt) returns a duration, ValueError is raised if tz.dst(dt) returns None (2.3a1 treated it as 0 instead, but a tzinfo subclass wishing to participate in time zone conversion has to take a stand on whether it supports DST; if you don't care about DST, then code dst() to return 0 minutes, meaning that DST is never in effect).

    The tzinfo methods utcoffset() and dst() must return a timedelta object (or None) now. In 2.3a1 they could also return an int or long, but that was an unhelpfully redundant leftover from an earlier version wherein they couldn't return a timedelta. TOOWTDI.

    The example tzinfo class for local time had a bug. It was replaced by a later example coded by Guido.

    datetime.astimezone(tz) no longer raises an exception when the input datetime has no UTC equivalent in tz. For typical "hybrid" time zones (a single tzinfo subclass modeling both standard and daylight time), this case can arise one hour per year, at the hour daylight time ends. See new docs for details. In short, the new behavior mimics the local wall clock's behavior of repeating an hour in local time.

    dt.astimezone() can no longer be used to convert between naive and aware datetime objects. If you merely want to attach, or remove, a tzinfo object, without any conversion of date and time members, use dt.replace(tzinfo=whatever) instead, where "whatever" is None or a tzinfo subclass instance.

    A new method tzinfo.fromutc(dt) can be overridden in tzinfo subclasses to give complete control over how a UTC time is to be converted to a local time. The default astimezone() implementation calls fromutc() as its last step, so a tzinfo subclass can affect that too by overriding fromutc(). It's expected that the default fromutc() implementation will be suitable as-is for "almost all" time zone subclasses, but the creativity of political time zone fiddling appears unbounded -- fromutc() allows the highly motivated to emulate any scheme expressible in Python. The optional tzinfo argument was undocumented (that's repaired), and its name was changed to tz ("tzinfo" is overloaded enough already). With a tz argument, now(tz) used to return the local date and time, and attach tz to it, without any conversion of date and time members. This was less than useful. Now now(tz) returns the current date and time as local time in tz's time zone, akin to


    where "utc" is an instance of a tzinfo subclass modeling UTC. Without a tz argument, now() continues to return the current local date and time, as a naive datetime object.

    datetime.fromtimestamp(): Like above, this had less than useful behavior when the optional tinzo argument was specified. See also SF bug report <>.

    date and datetime comparison: In order to prevent comparison from falling back to the default compare-object-addresses strategy, these raised TypeError whenever they didn't understand the other object type. They still do, except when the other object has a "timetuple" attribute, in which case they return NotImplemented now. This gives other datetime objects (e.g., mxDateTime) a chance to intercept the comparison.

    date, time, datetime and timedelta comparison: When the exception for mixed-type comparisons in the last paragraph doesn't apply, if the comparison is == then False is returned, and if the comparison is != then True is returned. Because dict lookup and the "in" operator only invoke __eq__, this allows, for example,

    if some_datetime in some_sequence:


    some_dict[some_timedelta] = whatever

    to work as expected, without raising TypeError just because the sequence is heterogeneous, or the dict has mixed-type keys. [This seems like a good idea to implement for all mixed-type comparisons that don't want to allow falling back to address comparison.]

    The constructors building a datetime from a timestamp could raise ValueError if the platform C localtime()/gmtime() inserted "leap seconds". Leap seconds are ignored now. On such platforms, it's possible to have timestamps that differ by a second, yet where datetimes constructed from them are equal.

    The pickle format of date, time and datetime objects has changed completely. The undocumented pickler and unpickler functions no longer exist. The undocumented __setstate__() and __getstate__() methods no longer exist either.


  • The logging module was updated slightly; the WARN level was renamed to WARNING, and the matching function/method warn() to warning().
  • The pickle and cPickle modules were updated with a new pickling protocol (documented by, see below) and several extensions to the pickle customization API (__reduce__, __setstate__ etc.). The copy module now uses more of the pickle customization API to copy objects that don't implement __copy__ or __deepcopy__. See PEP 307 for details.
  • The distutils "register" command now uses as the default repository. (See PEP 301.)
  • the platform dependent path related variables sep, altsep, extsep, pathsep, curdir, pardir and defpath are now defined in the platform dependent path modules (e.g. rather than, so these variables are now available via os.path. They continue to be available from the os module. (see <>).
  • array.array was added to the types knows about (see <>).
  • The new contains lots of documentation about pickle internals, and supplies some helpers for working with pickles, such as a symbolic pickle disassembler.
  • now supports the builtin boolean type.
  • py_compile has a new 'doraise' flag and a new PyCompileError exception.
  • SimpleXMLRPCServer now supports CGI through the CGIXMLRPCRequestHandler class.
  • The sets module now raises TypeError in __cmp__, to clarify that sets are not intended to be three-way-compared; the comparison operators are overloaded as subset/superset tests.
  • and are disabled. These modules are not safe in Python 2.2. or 2.3.
  • realpath is now exported when doing from poxixpath import *. It is also exported for ntpath, macpath, and os2emxpath. See SF bug #659228.
  • New module tarfile from Lars Gustהbel provides a comprehensive interface to tar archive files with transparent gzip and bzip2 compression. See SF patch #651082.
  • urlparse can now parse imap:// URLs. See SF feature request #618024.
  • Tkinter.Canvas.scan_dragto() provides an optional parameter to support the gain value which is passed to Tk. SF bug# 602259.
  • Fix logging.handlers.SysLogHandler protocol when using UNIX domain sockets. See SF patch #642974.
  • The dospath module was deleted. Use the ntpath module when manipulating DOS paths from other platforms.


  • Two new scripts ( and were added to the Tools/scripts directory to facilitate conversion from the old bsddb module to the new one. While the user-visible API of the new module is compatible with the old one, it's likely that the version of the underlying database library has changed. To convert from the old library, run the script using the old version of Python to convert it to a pickle file. After upgrading Python, run the script using the new version of Python to reconstitute your database. For example:

    % python2.2 -h some.db > some.pickle % python2.3 -h < some.pickle

    Run the scripts without any args to get a usage message.


  • The audio driver tests ( and are no longer run by default. This is because they don't always work, depending on your hardware and software. To run these tests, you must use an invocation like

    ./python Lib/test/ -u audio test_ossaudiodev
  • On systems which build using the configure script, compiler flags which used to be lumped together using the OPT flag have been split into two groups, OPT and BASECFLAGS. OPT is meant to carry just optimization- and debug-related flags like "-g" and "-O3". BASECFLAGS is meant to carry compiler flags that are required to get a clean compile. On some platforms (many Linux flavors in particular) BASECFLAGS will be empty by default. On others, such as Mac OS X and SCO, it will contain required flags. This change allows people building Python to override OPT without fear of clobbering compiler flags which are required to get a clean build.

  • On Darwin/Mac OS X platforms, /sw/lib and /sw/include are added to the relevant search lists in This allows users building Python to take advantage of the many packages available from the fink project <>.

  • A new Makefile target, scriptsinstall, installs a number of useful scripts from the Tools/scripts directory.


  • PyEval_GetFrame() is now declared to return a PyFrameObject * instead of a plain PyObject *. (SF patch #686601.)
  • PyNumber_Check() now checks that the object has a nb_int or nb_float slot, rather than simply checking whether it has a non-NULL tp_as_number pointer.
  • A C type that inherits from a base type that defines tp_as_buffer will now inherit the tp_as_buffer pointer if it doesn't define one. (SF #681367)
  • The PyArg_Parse functions now issue a DeprecationWarning if a float argument is provided when an integer is specified (this affects the 'b', 'B', 'h', 'H', 'i', and 'l' codes). Future versions of Python will raise a TypeError.


  • Several tests weren't being run from (,,,, and Now they are. (Note to developers: please read Lib/test/README when creating a new test, to make sure to do it right! All tests need to use either unittest or pydoc.)
  • Added, a test suite for the posix module.
  • Added, a test suite for hex/oct constant folding.


  • The timeout code for socket connect() didn't work right; this has now been fixed. should pass (at least most of the time).
  • distutils' msvccompiler class now passes the preprocessor options to the resource compiler. See SF patch #669198.
  • The bsddb module now ships with Sleepycat's 4.1.25.NC, the latest release without strong cryptography.
  • sys.path[0], if it contains a directory name, is now always an absolute pathname. (SF patch #664376.)
  • The new logging package is now installed by the Windows installer. It wasn't in 2.3a1 due to oversight.


  • There are new dialogs EasyDialogs.AskFileForOpen, AskFileForSave and AskFolder. The old macfs.StandardGetFile and friends are deprecated.
  • Most of the standard library now uses pathnames or FSRefs in preference of FSSpecs, and use the underlying Carbon.File and Carbon.Folder modules in stead of macfs. macfs will probably be deprecated in the future.
  • Type Carbon.File.FSCatalogInfo and supporting methods have been implemented. This also makes macfs.FSSpec.SetDates() work again.
  • There is a new module pimp, the package install manager for Python, and accompanying applet PackageManager. These allow you to easily download and install pretested extension packages either in source or binary form. Only in MacPython-OSX.
  • Applets are now built with bundlebuilder in MacPython-OSX, which should make them more robust and also provides a path towards BuildApplication. The downside of this change is that applets can no longer be run from the Terminal window, this will hopefully be fixed in the 2.3b1.

What's New in Python 2.3 alpha 1?

Release date: 31-Dec-2002

Type/class unification and new-style classes

  • One can now assign to __bases__ and __name__ of new-style classes.
  • dict() now accepts keyword arguments so that dict(one=1, two=2) is the equivalent of {"one": 1, "two": 2}. Accordingly, the existing (but undocumented) 'items' keyword argument has been eliminated. This means that dict(items=someMapping) now has a different meaning than before.
  • int() now returns a long object if the argument is outside the integer range, so int("4" * 1000), int(1e200) and int(1L<<1000) will all return long objects instead of raising an OverflowError.
  • Assignment to __class__ is disallowed if either the old or the new class is a statically allocated type object (such as defined by an extension module). This prevents anomalies like 2.__class__ = bool.
  • New-style object creation and deallocation have been sped up significantly; they are now faster than classic instance creation and deallocation.
  • The __slots__ variable can now mention "private" names, and the right thing will happen (e.g. __slots__ = ["__foo"]).
  • The built-ins slice() and buffer() are now callable types. The types classobj (formerly class), code, function, instance, and instancemethod (formerly instance-method), which have no built-in names but are accessible through the types module, are now also callable. The type dict-proxy is renamed to dictproxy.
  • Cycles going through the __class__ link of a new-style instance are now detected by the garbage collector.
  • Classes using __slots__ are now properly garbage collected. [SF bug 519621]
  • Tightened the __slots__ rules: a slot name must be a valid Python identifier.
  • The constructor for the module type now requires a name argument and takes an optional docstring argument. Previously, this constructor ignored its arguments. As a consequence, deriving a class from a module (not from the module type) is now illegal; previously this created an unnamed module, just like invoking the module type did. [SF bug 563060]
  • A new type object, 'basestring', is added. This is a common base type for 'str' and 'unicode', and can be used instead of types.StringTypes, e.g. to test whether something is "a string": isinstance(x, basestring) is True for Unicode and 8-bit strings. This is an abstract base class and cannot be instantiated directly.
  • Changed new-style class instantiation so that when C's __new__ method returns something that's not a C instance, its __init__ is not called. [SF bug #537450]
  • Fixed super() to work correctly with class methods. [SF bug #535444]
  • If you try to pickle an instance of a class that has __slots__ but doesn't define or override __getstate__, a TypeError is now raised. This is done by adding a bozo __getstate__ to the class that always raises TypeError. (Before, this would appear to be pickled, but the state of the slots would be lost.)

Core and builtins

  • Import from zipfiles is now supported. The name of a zipfile placed on sys.path causes the import statement to look for importable Python modules (with .py, pyc and .pyo extensions) and packages inside the zipfile. The zipfile import follows the specification (though not the sample implementation) of PEP 273. The semantics of __path__ are compatible with those that have been implemented in Jython since Jython 2.1.

  • PEP 302 has been accepted. Although it was initially developed to support zipimport, it offers a new, general import hook mechanism. Several new variables have been added to the sys module: sys.meta_path, sys.path_hooks, and sys.path_importer_cache; these make extending the import statement much more convenient than overriding the __import__ built-in function. For a description of these, see PEP 302.

  • A frame object's f_lineno attribute can now be written to from a trace function to change which line will execute next. A command to exploit this from pdb has been added. [SF patch #643835]

  • The _codecs support module for was turned into a builtin module to assure that at least the builtin codecs are available to the Python parser for source code decoding according to PEP 263.

  • issubclass now supports a tuple as the second argument, just like isinstance does. issubclass(X, (A, B)) is equivalent to issubclass(X, A) or issubclass(X, B).

  • Thanks to Armin Rigo, the last known way to provoke a system crash by cleverly arranging for a comparison function to mutate a list during a list.sort() operation has been fixed. The effect of attempting to mutate a list, or even to inspect its contents or length, while a sort is in progress, is not defined by the language. The C implementation of Python 2.3 attempts to detect mutations, and raise ValueError if one occurs, but there's no guarantee that all mutations will be caught, or that any will be caught across releases or implementations.

  • Unicode file name processing for Windows (PEP 277) is implemented. All platforms now have an os.path.supports_unicode_filenames attribute, which is set to True on Windows NT/2000/XP, and False elsewhere.

  • Codec error handling callbacks (PEP 293) are implemented. Error handling in unicode.encode or str.decode can now be customized.

  • A subtle change to the semantics of the built-in function intern(): interned strings are no longer immortal. You must keep a reference to the return value intern() around to get the benefit.

  • Use of 'None' as a variable, argument or attribute name now issues a SyntaxWarning. In the future, None may become a keyword.

  • SET_LINENO is gone. co_lnotab is now consulted to determine when to call the trace function. C code that accessed f_lineno should call PyCode_Addr2Line instead (f_lineno is still there, but only kept up to date when there is a trace function set).

  • There's a new warning category, FutureWarning. This is used to warn about a number of situations where the value or sign of an integer result will change in Python 2.4 as a result of PEP 237 (integer unification). The warnings implement stage B0 mentioned in that PEP. The warnings are about the following situations:

    • Octal and hex literals without 'L' prefix in the inclusive range [0x80000000..0xffffffff]; these are currently negative ints, but in Python 2.4 they will be positive longs with the same bit pattern.
    • Left shifts on integer values that cause the outcome to lose bits or have a different sign than the left operand. To be precise: x<<n where this currently doesn't yield the same value as long(x)<<n; in Python 2.4, the outcome will be long(x)<<n.
    • Conversions from ints to string that show negative values as unsigned ints in the inclusive range [0x80000000..0xffffffff]; this affects the functions hex() and oct(), and the string formatting codes %u, %o, %x, and %X. In Python 2.4, these will show signed values (e.g. hex(-1) currently returns "0xffffffff"; in Python 2.4 it will return "-0x1").
  • The bits manipulated under the cover by sys.setcheckinterval() have been changed. Both the check interval and the ticker used to be per-thread values. They are now just a pair of global variables. In addition, the default check interval was boosted from 10 to 100 bytecode instructions. This may have some effect on systems that relied on the old default value. In particular, in multi-threaded applications which try to be highly responsive, response time will increase by some (perhaps imperceptible) amount.

  • When multiplying very large integers, a version of the so-called Karatsuba algorithm is now used. This is most effective if the inputs have roughly the same size. If they both have about N digits, Karatsuba multiplication has O(N**1.58) runtime (the exponent is log_base_2(3)) instead of the previous O(N**2). Measured results may be better or worse than that, depending on platform quirks. Besides the O() improvement in raw instruction count, the Karatsuba algorithm appears to have much better cache behavior on extremely large integers (starting in the ballpark of a million bits). Note that this is a simple implementation, and there's no intent here to compete with, e.g., GMP. It gives a very nice speedup when it applies, but a package devoted to fast large-integer arithmetic should run circles around it.

  • u'%c' will now raise a ValueError in case the argument is an integer outside the valid range of Unicode code point ordinals.

  • The tempfile module has been overhauled for enhanced security. The mktemp() function is now deprecated; new, safe replacements are mkstemp() (for files) and mkdtemp() (for directories), and the higher-level functions NamedTemporaryFile() and TemporaryFile(). Use of some global variables in this module is also deprecated; the new functions have keyword arguments to provide the same functionality. All Lib, Tools and Demo modules that used the unsafe interfaces have been updated to use the safe replacements. Thanks to Zack Weinberg!

  • When x is an object whose class implements __mul__ and __rmul__, 1.0*x would correctly invoke __rmul__, but 1*x would erroneously invoke __mul__. This was due to the sequence-repeat code in the int type. This has been fixed now.

  • Previously, "str1 in str2" required str1 to be a string of length 1. This restriction has been relaxed to allow str1 to be a string of any length. Thus "'el' in 'hello world'" returns True now.

  • File objects are now their own iterators. For a file f, iter(f) now returns f (unless f is closed), and is similar to f.readline() when EOF is not reached; however, uses a readahead buffer that messes up the file position, so mixing and f.readline() (or other methods) doesn't work right. Calling drops the readahead buffer, but other operations don't. It so happens that this gives a nice additional speed boost to "for line in file:"; the xreadlines method and corresponding module are now obsolete. Thanks to Oren Tirosh!

  • Encoding declarations (PEP 263, phase 1) have been implemented. A comment of the form "# -- coding: <encodingname> --" in the first or second line of a Python source file indicates the encoding.

  • list.sort() has a new implementation. While cross-platform results may vary, and in data-dependent ways, this is much faster on many kinds of partially ordered lists than the previous implementation, and reported to be just as fast on randomly ordered lists on several major platforms. This sort is also stable (if A==B and A precedes B in the list at the start, A precedes B after the sort too), although the language definition does not guarantee stability. A potential drawback is that list.sort() may require temp space of len(list)*2 bytes (*4 on a 64-bit machine). It's therefore possible for list.sort() to raise MemoryError now, even if a comparison function does not. See <> for full details.

  • All standard iterators now ensure that, once StopIteration has been raised, all future calls to next() on the same iterator will also raise StopIteration. There used to be various counterexamples to this behavior, which could caused confusion or subtle program breakage, without any benefits. (Note that this is still an iterator's responsibility; the iterator framework does not enforce this.)

  • Ctrl+C handling on Windows has been made more consistent with other platforms. KeyboardInterrupt can now reliably be caught, and Ctrl+C at an interactive prompt no longer terminates the process under NT/2k/XP (it never did under Win9x). Ctrl+C will interrupt time.sleep() in the main thread, and any child processes created via the popen family (on win2k; we can't make win9x work reliably) are also interrupted (as generally happens on for Linux/Unix.) [SF bugs 231273, 439992 and 581232]

  • sys.getwindowsversion() has been added on Windows. This returns a tuple with information about the version of Windows currently running.

  • Slices and repetitions of buffer objects now consistently return a string. Formerly, strings would be returned most of the time, but a buffer object would be returned when the repetition count was one or when the slice range was all inclusive.

  • Unicode objects in sys.path are no longer ignored but treated as directory names.

  • Fixed string.startswith and string.endswith builtin methods so they accept negative indices. [SF bug 493951]

  • Fixed a bug with a continue inside a try block and a yield in the finally clause. [SF bug 567538]

  • Most builtin sequences now support "extended slices", i.e. slices with a third "stride" parameter. For example, "hello world"[::-1] gives "dlrow olleh".

  • A new warning PendingDeprecationWarning was added to provide direction on features which are in the process of being deprecated. The warning will not be printed by default. To see the pending deprecations, use -Walways::PendingDeprecationWarning:: as a command line option or warnings.filterwarnings() in code.

  • Deprecated features of xrange objects have been removed as promised. The start, stop, and step attributes and the tolist() method no longer exist. xrange repetition and slicing have been removed.

  • New builtin function enumerate(x), from PEP 279. Example: enumerate("abc") is an iterator returning (0,"a"), (1,"b"), (2,"c"). The argument can be an arbitrary iterable object.

  • The assert statement no longer tests __debug__ at runtime. This means that assert statements cannot be disabled by assigning a false value to __debug__.

  • A method zfill() was added to str and unicode, that fills a numeric string to the left with zeros. For example, "+123".zfill(6) -> "+00123".

  • Complex numbers supported divmod() and the // and % operators, but these make no sense. Since this was documented, they're being deprecated now.

  • String and unicode methods lstrip(), rstrip() and strip() now take an optional argument that specifies the characters to strip. For example, "Foo!!!?!?!?".rstrip("?!") -> "Foo".

  • There's a new dictionary constructor (a class method of the dict class), dict.fromkeys(iterable, value=None). It constructs a dictionary with keys taken from the iterable and all values set to a single value. It can be used for building sets and for removing duplicates from sequences.

  • Added a new dict method pop(key). This removes and returns the value corresponding to key. [SF patch #539949]

  • A new built-in type, bool, has been added, as well as built-in names for its two values, True and False. Comparisons and sundry other operations that return a truth value have been changed to return a bool instead. Read PEP 285 for an explanation of why this is backward compatible.

  • Fixed two bugs reported as SF #535905: under certain conditions, deallocating a deeply nested structure could cause a segfault in the garbage collector, due to interaction with the "trashcan" code; access to the current frame during destruction of a local variable could access a pointer to freed memory.

  • The optional object allocator ("pymalloc") has been enabled by default. The recommended practice for memory allocation and deallocation has been streamlined. A header file is included, Misc/pymemcompat.h, which can be bundled with 3rd party extensions and lets them use the same API with Python versions from 1.5.2 onwards.

  • PyErr_Display will provide file and line information for all exceptions that have an attribute print_file_and_line, not just SyntaxErrors.

  • The UTF-8 codec will now encode and decode Unicode surrogates correctly and without raising exceptions for unpaired ones.

  • Universal newlines (PEP 278) is implemented. Briefly, using 'U' instead of 'r' when opening a text file for reading changes the line ending convention so that any of 'r', 'rn', and 'n' is recognized (even mixed in one file); all three are converted to 'n', the standard Python line end character.

  • file.xreadlines() now raises a ValueError if the file is closed: Previously, an xreadlines object was returned which would raise a ValueError when the method was called.

  • sys.exit() inadvertently allowed more than one argument. An exception will now be raised if more than one argument is used.

  • Changed evaluation order of dictionary literals to conform to the general left to right evaluation order rule. Now {f1(): f2()} will evaluate f1 first.

  • Fixed bug #521782: when a file was in non-blocking mode, could silently lose data or wrongly throw an unknown error.

  • The sq_repeat, sq_inplace_repeat, sq_concat and sq_inplace_concat slots are now always tried after trying the corresponding nb_* slots. This fixes a number of minor bugs (see bug #624807).

  • Fix problem with dynamic loading on 64-bit AIX (see bug #639945).

Extension modules

  • Added three operators to the operator module:

    operator.pow(a,b) which is equivalent to: a**b. operator.is_(a,b) which is equivalent to: a is b. operator.is_not(a,b) which is equivalent to: a is not b.

  • posix.openpty now works on all systems that have /dev/ptmx.

  • A module zipimport exists to support importing code from zip archives.

  • The new datetime module supplies classes for manipulating dates and times. The basic design came from the Zope "fishbowl process", and favors practical commercial applications over calendar esoterica. See

  • _tkinter now returns Tcl objects, instead of strings. Objects which have Python equivalents are converted to Python objects, other objects are wrapped. This can be configured through the wantobjects method, or Tkinter.wantobjects.

  • The PyBSDDB wrapper around the Sleepycat Berkeley DB library has been added as the package bsddb. The traditional bsddb module is still available in source code, but not built automatically anymore, and is now named bsddb185. This supports Berkeley DB versions from 3.0 to 4.1. For help converting your databases from the old module (which probably used an obsolete version of Berkeley DB) to the new module, see the and scripts described in the Tools/Demos section above.

  • unicodedata was updated to Unicode 3.2. It supports normalization and names for Hangul syllables and CJK unified ideographs.

  • resource.getrlimit() now returns longs instead of ints.

  • readline now dynamically adjusts its input/output stream if sys.stdin/stdout changes.

  • The _tkinter module (and hence Tkinter) has dropped support for Tcl/Tk 8.0 and 8.1. Only Tcl/Tk versions 8.2, 8.3 and 8.4 are supported.

  • cPickle.BadPickleGet is now a class.

  • The time stamps in os.stat_result are floating point numbers after stat_float_times has been called.

  • If the size passed to mmap.mmap() is larger than the length of the file on non-Windows platforms, a ValueError is raised. [SF bug 585792]

  • The xreadlines module is slated for obsolescence.

  • The strptime function in the time module is now always available (a Python implementation is used when the C library doesn't define it).

  • The 'new' module is no longer an extension, but a Python module that only exists for backwards compatibility. Its contents are no longer functions but callable type objects.

  • The bsddb.*open functions can now take 'None' as a filename. This will create a temporary in-memory bsddb that won't be written to disk.

  • posix.getloadavg, posix.lchown, posix.killpg, posix.mknod, and posix.getpgid have been added where available.

  • The locale module now exposes the C library's gettext interface. It also has a new function getpreferredencoding.

  • A security hole ("double free") was found in zlib-1.1.3, a popular third party compression library used by some Python modules. The hole was quickly plugged in zlib-1.1.4, and the Windows build of Python now ships with zlib-1.1.4.

  • pwd, grp, and resource return enhanced tuples now, with symbolic field names.

  • array.array is now a type object. A new format character 'u' indicates Py_UNICODE arrays. For those, .tounicode and .fromunicode methods are available. Arrays now support __iadd__ and __imul__.

  • dl now builds on every system that has dlfcn.h. Failure in case of sizeof(int)!=sizeof(long)!=sizeof(void*) is delayed until is called.

  • The sys module acquired a new attribute, api_version, which evaluates to the value of the PYTHON_API_VERSION macro with which the interpreter was compiled.

  • Fixed bug #470582: sre module would return a tuple (None, 'a', 'ab') when applying the regular expression '^((a)c)?(ab)$' on 'ab'. It now returns (None, None, 'ab'), as expected. Also fixed handling of lastindex/lastgroup match attributes in similar cases. For example, when running the expression r'(a)(b)?b' over 'ab', lastindex must be 1, not 2.

  • Fixed bug #581080: sre scanner was not checking the buffer limit before increasing the current pointer. This was creating an infinite loop in the search function, once the pointer exceeded the buffer limit.

  • The os.fdopen function now enforces a file mode starting with the letter 'r', 'w' or 'a', otherwise a ValueError is raised. This fixes bug #623464.

  • The linuxaudiodev module is now deprecated; it is being replaced by ossaudiodev. The interface has been extended to cover a lot more of OSS (see, including most DSP ioctls and the OSS mixer API. Documentation forthcoming in 2.3a2.


  • now supports SSL (Tino Lange and Piers Lauder).

  • Freeze's has been moved to the standard library; slightly improved so it will issue less false missing submodule reports (see sf path #643711 for details). Documentation will follow with Python 2.3a2.

  • os.path exposes getctime.

  • now has two additional methods called assertAlmostEqual() and failIfAlmostEqual(). They implement an approximate comparison by rounding the difference between the two arguments and comparing the result to zero. Approximate comparison is essential for unit tests of floating point results.

  • now depends on the new datetime module rather than the time module. As a result, the range of allowable dates has been increased.

  • pdb has a new 'j(ump)' command to select the next line to be executed.

  • The distutils created windows installers now can run a postinstallation script.

  • doctest.testmod can now be called without argument, which means to test the current module.

  • When canceling a server that implemented threading with a keyboard interrupt, the server would shut down but not terminate (waiting on client threads). A new member variable, daemon_threads, was added to the ThreadingMixIn class in to make it explicit that this behavior needs to be controlled.

  • A new module, optparse, provides a fancy alternative to getopt for command line parsing. It is a slightly modified version of Greg Ward's Optik package.

  • now defines a DictMixin class which defines all dictionary methods for classes that already have a minimum mapping interface. This greatly simplifies writing classes that need to be substitutable for dictionaries (such as the shelve module).

  • now subclasses from UserDict.DictMixin. Now shelve supports all dictionary methods. This eases the transition to persistent storage for scripts originally written with dictionaries in mind.

  • and the various classes in now accept an optional binary flag, which defaults to False. If True, the values stored in the shelf are binary pickles.

  • A new package, logging, implements the logging API defined by PEP 282. The code is written by Vinay Sajip.

  • StreamReader, StreamReaderWriter and StreamRecoder in the codecs modules are iterators now.

  • now handles files exceeding 2GB. Files over 4GB also work now (provided the OS supports it, and Python is configured with large file support), but in that case the underlying gzip file format can record only the least-significant 32 bits of the file size, so that some tools working with gzipped files may report an incorrect file size.

  • xml.sax.saxutils.unescape has been added, to replace entity references with their entity value.

  • Queue.Queue.{put,get} now support an optional timeout argument.

  • Various features of Tk 8.4 are exposed in The multiple option of tkFileDialog is exposed as function askopenfile{,name}s.

  • Various configure methods of Tkinter have been stream-lined, so that tag_configure, image_configure, window_configure now return a dictionary when invoked with no argument.

  • Importing the readline module now no longer has the side effect of calling setlocale(LC_CTYPE, ""). The initial "C" locale, or whatever locale is explicitly set by the user, is preserved. If you want repr() of 8-bit strings in your preferred encoding to preserve all printable characters of that encoding, you have to add the following code to your $PYTHONSTARTUP file or to your application's main():

    import locale locale.setlocale(locale.LC_CTYPE, "")

  • shutil.move was added. shutil.copytree now reports errors as an exception at the end, instead of printing error messages.

  • Encoding name normalization was generalized to not only replace hyphens with underscores, but also all other non-alphanumeric characters (with the exception of the dot which is used for Python package names during lookup). The mapping was updated to the new standard.

  • mimetypes has two new functions: guess_all_extensions() which returns a list of all known extensions for a mime type, and add_type() which adds one mapping between a mime type and an extension to the database.

  • New module: sets, defines the class Set that implements a mutable set type using the keys of a dict to represent the set. There's also a class ImmutableSet which is useful when you need sets of sets or when you need to use sets as dict keys, and a class BaseSet which is the base class of the two.

  • Added random.sample(population,k) for random sampling without replacement. Returns a k length list of unique elements chosen from the population.

  • random.randrange(-sys.maxint-1, sys.maxint) no longer raises OverflowError. That is, it now accepts any combination of 'start' and 'stop' arguments so long as each is in the range of Python's bounded integers.

  • Thanks to Raymond Hettinger, random.random() now uses a new core generator. The Mersenne Twister algorithm is implemented in C, threadsafe, faster than the previous generator, has an astronomically large period (2**19937-1), creates random floats to full 53-bit precision, and may be the most widely tested random number generator in existence.

    The random.jumpahead(n) method has different semantics for the new generator. Instead of jumping n steps ahead, it uses n and the existing state to create a new state. This means that jumpahead() continues to support multi-threaded code needing generators of non-overlapping sequences. However, it will break code which relies on jumpahead moving a specific number of steps forward.

    The attributes random.whseed and random.__whseed have no meaning for the new generator. Code using these attributes should switch to a new class, random.WichmannHill which is provided for backward compatibility and to make an alternate generator available.

  • New "algorithms" module: heapq, implements a heap queue. Thanks to Kevin O'Connor for the code and Franחois Pinard for an entertaining write-up explaining the theory and practical uses of heaps.

  • New encoding for the Palm OS character set: palmos.

  • binascii.crc32() and the zipfile module had problems on some 64-bit platforms. These have been fixed. On a platform with 8-byte C longs, crc32() now returns a signed-extended 4-byte result, so that its value as a Python int is equal to the value computed a 32-bit platform.

  • xml.dom.minidom.toxml and toprettyxml now take an optional encoding argument.

  • Some fixes in the copy module: when an object is copied through its __reduce__ method, there was no check for a __setstate__ method on the result [SF patch 565085]; deepcopy should treat instances of custom metaclasses the same way it treats instances of type 'type' [SF patch 560794].

  • Sockets now support timeout mode. After s.settimeout(T), where T is a float expressing seconds, subsequent operations raise an exception if they cannot be completed within T seconds. To disable timeout mode, use s.settimeout(None). There's also a module function, socket.setdefaulttimeout(T), which sets the default for all sockets created henceforth.

  • getopt.gnu_getopt was added. This supports GNU-style option processing, where options can be mixed with non-option arguments.

  • Stop using strings for exceptions. String objects used for exceptions are now classes deriving from Exception. The objects changed were: Tkinter.TclError, bdb.BdbQuit, macpath.norm_error, tabnanny.NannyNag, and xdrlib.Error.

  • Constants BOM_UTF8, BOM_UTF16, BOM_UTF16_LE, BOM_UTF16_BE, BOM_UTF32, BOM_UTF32_LE and BOM_UTF32_BE that represent the Byte Order Mark in UTF-8, UTF-16 and UTF-32 encodings for little and big endian systems were added to the codecs module. The old names BOM32_* and BOM64_* were off by a factor of 2.

  • Added conversion functions math.degrees() and math.radians().

  • math.log() now takes an optional argument: math.log(x[, base]).

  • ftplib.retrlines() now tests for callback is None rather than testing for False. Was causing an error when given a callback object which was callable but also returned len() as zero. The change may create new breakage if the caller relied on the undocumented behavior and called with callback set to [] or some other False value not identical to None.

  • random.gauss() uses a piece of hidden state used by nothing else, and the .seed() and .whseed() methods failed to reset it. In other words, setting the seed didn't completely determine the sequence of results produced by random.gauss(). It does now. Programs repeatedly mixing calls to a seed method with calls to gauss() may see different results now.

  • The pickle.Pickler class grew a clear_memo() method to mimic that provided by cPickle.Pickler.

  • difflib's SequenceMatcher class now does a dynamic analysis of which elements are so frequent as to constitute noise. For comparing files as sequences of lines, this generally works better than the IS_LINE_JUNK function, and function ndiff's linejunk argument defaults to None now as a result. A happy benefit is that SequenceMatcher may run much faster now when applied to large files with many duplicate lines (for example, C program text with lots of repeated "}" and "return NULL;" lines).

  • New Text.dump() method in Tkinter module.

  • New distutils commands for building packagers were added to support pkgtool on Solaris and swinstall on HP-UX.

  • distutils now has a new abstract binary packager base class command/bdist_packager, which simplifies writing packagers. This will hopefully provide the missing bits to encourage people to submit more packagers, e.g. for Debian, FreeBSD and other systems.

  • The UTF-16, -LE and -BE stream readers now raise a NotImplementedError for all calls to .readline(). Previously, they used to just produce garbage or fail with an encoding error -- UTF-16 is a 2-byte encoding and the C lib's line reading APIs don't work well with these.

  • compileall now supports quiet operation.

  • The BaseHTTPServer now implements optional HTTP/1.1 persistent connections.

  • socket module: the SSL support was broken out of the main _socket module C helper and placed into a new _ssl helper which now gets imported by if available and working.

  • encodings package: added aliases for all supported IANA character sets

  • ftplib: to safeguard the user's privacy, anonymous login will use "anonymous@" as default password, rather than the real user and host name.

  • webbrowser: tightened up the command passed to os.system() so that arbitrary shell code can't be executed because a bogus URL was passed in.

  • gettext.translation has an optional fallback argument, and gettext.find an optional all argument. Translations will now fallback on a per-message basis. The module supports plural forms, by means of gettext.[d]ngettext and Translation.[u]ngettext.

  • distutils bdist commands now offer a --skip-build option.

  • warnings.warn now accepts a Warning instance as first argument.

  • The xml.sax.expatreader.ExpatParser class will no longer create circular references by using itself as the locator that gets passed to the content handler implementation. [SF bug #535474]

  • The email.Parser.Parser class now properly parses strings regardless of their line endings, which can be any of r, n, or rn (CR, LF, or CRLF). Also, the Header class's constructor default arguments has changed slightly so that an explicit maxlinelen value is always honored, and so unicode conversion error handling can be specified.

  • distutils' build_ext command now links C++ extensions with the C++ compiler available in the Makefile or CXX environment variable, if running under *nix.

  • New module bz2: provides a comprehensive interface for the bz2 compression library. It implements a complete file interface, one-shot (de)compression functions, and types for sequential (de)compression.

  • New pdb command 'pp' which is like 'p' except that it pretty-prints the value of its expression argument.

  • Now bdist_rpm distutils command understands a verify_script option in the config file, including the contents of the referred filename in the "%verifyscript" section of the rpm spec file.

  • Fixed bug #495695: webbrowser module would run graphic browsers in a unix environment even if DISPLAY was not set. Also, support for skipstone browser was included.

  • Fixed bug #636769: rexec would run disallowed code if subclasses of strings were used as parameters for certain functions.


  • now supports globbing on Windows, and accepts module names in addition to accepting file names.
  • The SGI demos (Demo/sgi) have been removed. Nobody thought they were interesting any more. (The SGI library modules and extensions are still there; it is believed that at least some of these are still used and useful.)
  • IDLE supports the new encoding declarations (PEP 263); it can also deal with legacy 8-bit files if they use the locale's encoding. It allows non-ASCII strings in the interactive shell and executes them in the locale's encoding.
  • now produces binaries which can import shared modules, unlike before when this failed due to missing symbol exports in the generated binary.


  • On Unix, IDLE is now installed automatically.

  • The fpectl module is not built by default; it's dangerous or useless except in the hands of experts.

  • The public Python C API will generally be declared using PyAPI_FUNC and PyAPI_DATA macros, while Python extension module init functions will be declared with PyMODINIT_FUNC. DL_EXPORT/DL_IMPORT macros are deprecated.

  • A bug was fixed that could cause COUNT_ALLOCS builds to segfault, or get into infinite loops, when a new-style class got garbage-collected. Unfortunately, to avoid this, the way COUNT_ALLOCS works requires that new-style classes be immortal in COUNT_ALLOCS builds. Note that COUNT_ALLOCS is not enabled by default, in either release or debug builds, and that new-style classes are immortal only in COUNT_ALLOCS builds.

  • Compiling out the cyclic garbage collector is no longer an option. The old symbol WITH_CYCLE_GC is now ignored, and Python.h arranges that it's always defined (for the benefit of any extension modules that may be conditionalizing on it). A bonus is that any extension type participating in cyclic gc can choose to participate in the Py_TRASHCAN mechanism now too; in the absence of cyclic gc, this used to require editing the core to teach the trashcan mechanism about the new type.

  • According to Annex F of the current C standard,

    The Standard C macro HUGE_VAL and its float and long double analogs, HUGE_VALF and HUGE_VALL, expand to expressions whose values are positive infinities.

    Python only uses the double HUGE_VAL, and only to #define its own symbol Py_HUGE_VAL. Some platforms have incorrect definitions for HUGE_VAL. pyport.h used to try to worm around that, but the workarounds triggered other bugs on other platforms, so we gave up. If your platform defines HUGE_VAL incorrectly, you'll need to #define Py_HUGE_VAL to something that works on your platform. The only instance of this I'm sure about is on an unknown subset of Cray systems, described here:

    Presumably 2.3a1 breaks such systems. If anyone uses such a system, help!

  • The configure option --without-doc-strings can be used to remove the doc strings from the builtin functions and modules; this reduces the size of the executable.

  • The universal newlines option (PEP 278) is on by default. On Unix it can be disabled by passing --without-universal-newlines to the configure script. On other platforms, remove WITH_UNIVERSAL_NEWLINES from pyconfig.h.

  • On Unix, a shared can be created with --enable-shared.

  • All uses of the CACHE_HASH, INTERN_STRINGS, and DONT_SHARE_SHORT_STRINGS preprocessor symbols were eliminated. The internal decisions they controlled stopped being experimental long ago.

  • The tools used to build the documentation now work under Cygwin as well as Unix.

  • The bsddb and dbm module builds have been changed to try and avoid version skew problems and disable linkage with Berkeley DB 1.85 unless the installer knows what s/he's doing. See the section on building these modules in the README file for details.


  • PyNumber_Check() now returns true for string and unicode objects. This is a result of these types having a partially defined tp_as_number slot. (This is not a feature, but an indication that PyNumber_Check() is not very useful to determine numeric behavior. It may be deprecated.)
  • The string object's layout has changed: the pointer member ob_sinterned has been replaced by an int member ob_sstate. On some platforms (e.g. most 64-bit systems) this may change the offset of the ob_sval member, so as a precaution the API_VERSION has been incremented. The apparently unused feature of "indirect interned strings", supported by the ob_sinterned member, is gone. Interned strings are now usually mortal; there is a new API, PyString_InternImmortal() that creates immortal interned strings. (The ob_sstate member can only take three values; however, while making it a char saves a few bytes per string object on average, in it also slowed things down a bit because ob_sval was no longer aligned.)
  • The Py_InitModule*() functions now accept NULL for the 'methods' argument. Modules without global functions are becoming more common now that factories can be types rather than functions.
  • New C API PyUnicode_FromOrdinal() which exposes unichr() at C level.
  • New functions PyErr_SetExcFromWindowsErr() and PyErr_SetExcFromWindowsErrWithFilename(). Similar to PyErr_SetFromWindowsErrWithFilename() and PyErr_SetFromWindowsErr(), but they allow to specify the exception type to raise. Available on Windows.
  • Py_FatalError() is now declared as taking a const char* argument. It was previously declared without const. This should not affect working code.
  • Added new macro PySequence_ITEM(o, i) that directly calls sq_item without rechecking that o is a sequence and without adjusting for negative indices.
  • PyRange_New() now raises ValueError if the fourth argument is not 1. This is part of the removal of deprecated features of the xrange object.
  • PyNumber_Coerce() and PyNumber_CoerceEx() now also invoke the type's coercion if both arguments have the same type but this type has the CHECKTYPES flag set. This is to better support proxies.
  • The type of tp_free has been changed from "void (*)(PyObject *)" to "void (*)(void *)".
  • PyObject_Del, PyObject_GC_Del are now functions instead of macros.
  • A type can now inherit its metatype from its base type. Previously, when PyType_Ready() was called, if ob_type was found to be NULL, it was always set to &PyType_Type; now it is set to base->ob_type, where base is tp_base, defaulting to &PyObject_Type.
  • PyType_Ready() accidentally did not inherit tp_is_gc; now it does.
  • The PyCore_* family of APIs have been removed.
  • The "u#" parser marker will now pass through Unicode objects as-is without going through the buffer API.
  • The enumerators of cmp_op have been renamed to use the prefix PyCmp_.
  • An old #define of ANY as void has been removed from pyport.h. This hasn't been used since Python's pre-ANSI days, and the #define has been marked as obsolete since then. SF bug 495548 says it created conflicts with other packages, so keeping it around wasn't harmless.
  • Because Python's magic number scheme broke on January 1st, we decided to stop Python development. Thanks for all the fish!
  • Some of us don't like fish, so we changed Python's magic number scheme to a new one. See Python/import.c for details.

New platforms

  • OpenVMS is now supported.
  • AtheOS is now supported.
  • the EMX runtime environment on OS/2 is now supported.
  • GNU/Hurd is now supported.


  • The script's -u option now provides a way to say "allow all resources except this one." For example, to allow everything except bsddb, give the option '-uall,-bsddb'.


  • The Windows distribution now ships with version 4.0.14 of the Sleepycat Berkeley database library. This should be a huge improvement over the previous Berkeley DB 1.85, which had many bugs. XXX What are the licensing issues here? XXX If a user has a database created with a previous version of XXX Python, what must they do to convert it? XXX I'm still not sure how to link this thing (see PCbuild/readme.txt). XXX The version # is likely to change before 2.3a1.

  • The Windows distribution now ships with a Secure Sockets Library (SLL)

    module (_ssl.pyd)

  • The Windows distribution now ships with Tcl/Tk version 8.4.1 (it previously shipped with Tcl/Tk 8.3.2).

  • When Python is built under a Microsoft compiler, sys.version now includes the compiler version number (_MSC_VER). For example, under MSVC 6, sys.version contains the substring "MSC v.1200 ". 1200 is the value of _MSC_VER under MSVC 6.

  • Sometimes the uninstall executable (UNWISE.EXE) vanishes. One cause of that has been fixed in the installer (disabled Wise's "delete in- use files" uninstall option).

  • Fixed a bug in urllib's proxy handling in Windows. [SF bug #503031]

  • The installer now installs Start menu shortcuts under (the local equivalent of) "All Users" when doing an Admin install.

  • file.truncate([newsize]) now works on Windows for all newsize values. It used to fail if newsize didn't fit in 32 bits, reflecting a limitation of MS _chsize (which is no longer used).

  • os.waitpid() is now implemented for Windows, and can be used to block until a specified process exits. This is similar to, but not exactly the same as, os.waitpid() on POSIX systems. If you're waiting for a specific process whose pid was obtained from one of the spawn() functions, the same Python os.waitpid() code works across platforms. See the docs for details. The docs were changed to clarify that spawn functions return, and waitpid requires, a process handle on Windows (not the same thing as a Windows process id).

  • New tempfile.TemporaryFile implementation for Windows: this doesn't need a TemporaryFileWrapper wrapper anymore, and should be immune to a nasty problem: before 2.3, if you got a temp file on Windows, it got wrapped in an object whose close() method first closed the underlying file, then deleted the file. This usually worked fine. However, the spawn family of functions on Windows create (at a low C level) the same set of open files in the spawned process Q as were open in the spawning process P. If a temp file f was among them, then doing f.close() in P first closed P's C-level file handle on f, but Q's C-level file handle on f remained open, so the attempt in P to delete f blew up with a "Permission denied" error (Windows doesn't allow deleting open files). This was surprising, subtle, and difficult to work around.

  • The os module now exports all the symbolic constants usable with the low-level on Windows: the new constants in 2.3 are O_NOINHERIT, O_SHORT_LIVED, O_TEMPORARY, O_RANDOM and O_SEQUENTIAL. The others were also available in 2.2: O_APPEND, O_BINARY, O_CREAT, O_EXCL, O_RDONLY, O_RDWR, O_TEXT, O_TRUNC and O_WRONLY. Contrary to Microsoft docs, O_SHORT_LIVED does not seem to imply O_TEMPORARY (so specify both if you want both; note that neither is useful unless specified with O_CREAT too).


  • Mac/Relnotes is gone, the release notes are now here.
  • Python (the OSX-only, unix-based version, not the OS9-compatible CFM version) now fully supports unicode strings as arguments to various file system calls, eg. open(), file(), os.stat() and os.listdir().
  • The current naming convention for Python on the Macintosh is that MacPython refers to the unix-based OSX-only version, and MacPython-OS9 refers to the CFM-based version that runs on both OS9 and OSX.
  • All MacPython-OS9 functionality is now available in an OSX unix build, including the Carbon modules, the IDE, OSA support, etc. A lot of this will only work correctly in a framework build, though, because you cannot talk to the window manager unless your application is run from a .app bundle. There is a command line tool "pythonw" that runs your script with an interpreter living in such a .app bundle, this interpreter should be used to run any Python script using the window manager (including Tkinter or wxPython scripts).
  • Most of Mac/Lib has moved to Lib/plat-mac, which is again used both in MacPython-OSX and MacPython-OS9. The only modules remaining in Mac/Lib are specifically for MacPython-OS9 (CFM support, preference resources, etc).
  • A new utility PythonLauncher will start a Python interpreter when a .py or .pyw script is double-clicked in the Finder. By default .py scripts are run with a normal Python interpreter in a Terminal window and .pyw files are run with a window-aware pythonw interpreter without a Terminal window, but all this can be customized.
  • MacPython-OS9 is now Carbon-only, so it runs on Mac OS 9 or Mac OS X and possibly on Mac OS 8.6 with the right CarbonLib installed, but not on earlier releases.
  • Many tools such as and now support a command line interface too.
  • All the Carbon classes are now PEP253 compliant, meaning that you can subclass them from Python. Most of the attributes have gone, you should now use the accessor function call API, which is also what Apple's documentation uses. Some attributes such as grafport.visRgn are still available for convenience.
  • New Carbon modules File (implementing the APIs in Files.h and Aliases.h) and Folder (APIs from Folders.h). The old macfs builtin module is gone, and replaced by a Python wrapper around the new modules.
  • Pathname handling should now be fully consistent: MacPython-OSX always uses unix pathnames and MacPython-OS9 always uses colon-separated Mac pathnames (also when running on Mac OS X).
  • New Carbon modules Help and AH give access to the Carbon Help Manager. There are hooks in the IDE to allow accessing the Python documentation (and Apple's Carbon and Cocoa documentation) through the Help Viewer. See Mac/OSX/README for converting the Python documentation to a Help Viewer compatible form and installing it.
  • OSA support has been redesigned and the generated Python classes now mirror the inheritance defined by the underlying OSA classes.
  • MacPython no longer maps both r and n to n on input for any text file. This feature has been replaced by universal newline support (PEP278).
  • The default encoding for Python sourcefiles in MacPython-OS9 is no longer mac-roman (or whatever your local Mac encoding was) but "ascii", like on other platforms. If you really need sourcefiles with Mac characters in them you can change this in

What's New in Python 2.2 final?

Release date: 21-Dec-2001

Type/class unification and new-style classes

  •, cPickle: allow pickling instances of new-style classes with a custom metaclass.

Core and builtins

  • weakref proxy object: when comparing, unwrap both arguments if both are proxies.

Extension modules

  • binascii.b2a_base64(): fix a potential buffer overrun when encoding very short strings.
  • cPickle: the obscure "fast" mode was suspected of causing stack overflows on the Mac. Hopefully fixed this by setting the recursion limit much smaller. If the limit is too low (it only affects performance), you can change it by defining PY_CPICKLE_FAST_LIMIT when compiling cPickle.c (or in pyconfig.h).


  • fixed a dumb old bug (the file didn't get synched at close or delete time).
  • fixed a bug where the address '<>' was converted to None instead of an empty string (also fixes the email.Utils module).
  • version 1.0.0; uses precision for doubles.
  • test suite: the pickle and cPickle tests were not executing any code when run from the standard regression test.




New platforms



  • distutils package: fixed broken Windows installers (bdist_wininst).
  • prevent mysterious warnings when TemporaryFileWrapper instances are deleted at process exit time.
  • prevent mysterious warnings when socket instances are deleted at process exit time.
  • posixmodule.c: fix a Windows crash with stat() of a filename ending in backslash.


  • The Carbon toolbox modules have been upgraded to Universal Headers 3.4, and experimental CoreGraphics and CarbonEvents modules have been added. All only for framework-enabled MacOSX.

What's New in Python 2.2c1?

Release date: 14-Dec-2001

Type/class unification and new-style classes

  • Guido's tutorial introduction to the new type/class features has been extensively updated. See

    That remains the primary documentation in this area.

  • Fixed a leak: instance variables declared with __slots__ were never deleted!

  • The "delete attribute" method of descriptor objects is called __delete__, not __del__. In previous releases, it was mistakenly called __del__, which created an unfortunate overloading condition with finalizers. (The "get attribute" and "set attribute" methods are still called __get__ and __set__, respectively.)

  • Some subtle issues with the super built-in were fixed:

    1. When super itself is subclassed, its __get__ method would still return an instance of the base class (i.e., of super).
    2. super(C, C()).__class__ would return C rather than super. This is confusing. To fix this, I decided to change the semantics of super so that it only applies to code attributes, not to data attributes. After all, overriding data attributes is not supported anyway.
    3. The __get__ method didn't check whether the argument was an instance of the type used in creation of the super instance.
  • Previously, hash() of an instance of a subclass of a mutable type (list or dictionary) would return some value, rather than raising TypeError. This has been fixed. Also, directly calling dict.__hash__ and list.__hash__ now raises the same TypeError (previously, these were the same as object.__hash__).

  • New-style objects now support deleting their __dict__. This is for all intents and purposes equivalent to assigning a brand new empty dictionary, but saves space if the object is not used further.

Core and builtins

  • -Qnew now works as documented in PEP 238: when -Qnew is passed on the command line, all occurrences of "/" use true division instead of classic division. See the PEP for details. Note that "all" means all instances in library and 3rd-party modules, as well as in your own code. As the PEP says, -Qnew is intended for use only in educational environments with control over the libraries in use. Note that in the standard Python test suite fails under -Qnew; this is expected, and won't be repaired until true division becomes the default (in the meantime, test_coercion is testing the current rules).
  • complex() now only allows the first argument to be a string argument, and raises TypeError if either the second arg is a string or if the second arg is specified when the first is a string.

Extension modules

  • gc.get_referents was renamed to gc.get_referrers.


  • Functions in the os.spawn() family now release the global interpreter lock around calling the platform spawn. They should always have done this, but did not before 2.2c1. Multithreaded programs calling an os.spawn function with P_WAIT will no longer block all Python threads until the spawned program completes. It's possible that some programs relies on blocking, although more likely by accident than by design.
  • webbrowser defaults to netscape.exe on OS/2 now.
  • Tix.ResizeHandle exposes detach_widget, hide, and show.
  • The charset alias windows_1252 has been added.
  • types.StringTypes is a tuple containing the defined string types; usually this will be (str, unicode), but if Python was compiled without Unicode support it will be just (str,).
  • The pulldom and minidom modules were synchronized to PyXML.


  • A new script called Tools/scripts/ was added, which fires off a search on Google.


  • Note that release builds of Python should arrange to define the preprocessor symbol NDEBUG on the command line (or equivalent). In the 2.2 pre-release series we tried to define this by magic in Python.h instead, but it proved to cause problems for extension authors. The Unix, Windows and Mac builds now all define NDEBUG in release builds via cmdline (or equivalent) instead. Ports to other platforms should do likewise.
  • It is no longer necessary to use --with-suffix when building on a case-insensitive file system (such as Mac OS X HFS+). In the build directory an extension is used, but not in the installed python.


  • New function PyDict_MergeFromSeq2() exposes the builtin dict constructor's logic for updating a dictionary from an iterable object producing key-value pairs.
  • PyArg_ParseTupleAndKeywords() requires that the number of entries in the keyword list equal the number of argument specifiers. This wasn't checked correctly, and PyArg_ParseTupleAndKeywords could even dump core in some bad cases. This has been repaired. As a result, PyArg_ParseTupleAndKeywords may raise RuntimeError in bad cases that previously went unchallenged.

New platforms




  • In unix-Python on Mac OS X (and darwin) sys.platform is now "darwin", without any trailing digits.
  • Changed logic for finding python home in Mac OS X framework Pythons. Now sys.executable points to the executable again, in stead of to the shared library. The latter is used only for locating the python home.

What's New in Python 2.2b2?

Release date: 16-Nov-2001

Type/class unification and new-style classes

  • Multiple inheritance mixing new-style and classic classes in the list of base classes is now allowed, so this works now:

    class Classic: pass class Mixed(Classic, object): pass

    The MRO (method resolution order) for each base class is respected according to its kind, but the MRO for the derived class is computed using new-style MRO rules if any base class is a new-style class. This needs to be documented.

  • The new builtin dictionary() constructor, and dictionary type, have been renamed to dict. This reflects a decade of common usage.

  • dict() now accepts an iterable object producing 2-sequences. For example, dict(d.items()) == d for any dictionary d. The argument, and the elements of the argument, can be any iterable objects.

  • New-style classes can now have a __del__ method, which is called when the instance is deleted (just like for classic classes).

  • Assignment to object.__dict__ is now possible, for objects that are instances of new-style classes that have a __dict__ (unless the base class forbids it).

  • Methods of built-in types now properly check for keyword arguments (formerly these were silently ignored). The only built-in methods that take keyword arguments are __call__, __init__ and __new__.

  • The socket function has been converted to a type; see below.

Core and builtins

  • Assignment to __debug__ raises SyntaxError at compile-time. This was promised when 2.1c1 was released as "What's New in Python 2.1c1" (see below) says.
  • Clarified the error messages for unsupported operands to an operator (like 1 + '').

Extension modules

  • mmap has a new keyword argument, "access", allowing a uniform way for both Windows and Unix users to create read-only, write-through and copy-on-write memory mappings. This was previously possible only on Unix. A new keyword argument was required to support this in a uniform way because the mmap() signatures had diverged across platforms. Thanks to Jay T Miller for repairing this!
  • By default, the gc.garbage list now contains only those instances in unreachable cycles that have __del__ methods; in 2.1 it contained all instances in unreachable cycles. "Instances" here has been generalized to include instances of both new-style and old-style classes.
  • The socket module defines a new method for socket objects, sendall(). This is like send() but may make multiple calls to send() until all data has been sent. Also, the socket function has been converted to a subclassable type, like list and tuple (etc.) before it; socket and SocketType are now the same thing.
  • Various bugfixes to the curses module. There is now a test suite for the curses module (you have to run it manually).
  • binascii.b2a_base64 no longer places an arbitrary restriction of 57 bytes on its input.


  • tkFileDialog exposes a Directory class and askdirectory convenience function.
  • Symbolic group names in regular expressions must be unique. For example, the regexp r'(?P<abc>)(?P<abc>)' is not allowed, because a single name can't mean both "group 1" and "group 2" simultaneously. Python 2.2 detects this error at regexp compilation time; previously, the error went undetected, and results were unpredictable. Also in sre, the pattern.split(), pattern.sub(), and pattern.subn() methods have been rewritten in C. Also, an experimental function/method finditer() has been added, which works like findall() but returns an iterator.
  • Tix exposes more commands through the classes DirSelectBox, DirSelectDialog, ListNoteBook, Meter, CheckList, and the methods tix_addbitmapdir, tix_cget, tix_configure, tix_filedialog, tix_getbitmap, tix_getimage, tix_option_get, and tix_resetoptions.
  • Traceback objects are now scanned by cyclic garbage collection, so cycles created by casual use of sys.exc_info() no longer cause permanent memory leaks (provided garbage collection is enabled).
  • os.extsep -- a new variable needed by the RISCOS support. It is the separator used by extensions, and is '.' on all platforms except RISCOS, where it is '/'. There is no need to use this variable unless you have a masochistic desire to port your code to RISCOS.
  • has optional support for non-standard, but commonly found types. guess_type() and guess_extension() now accept an optional 'strict' flag, defaulting to true, which controls whether recognize non-standard types or not. A few non-standard types we know about have been added. Also, when run as a script, there are new -l and -e options.
  • statcache is now deprecated.
  • email.Utils.formatdate() now produces the preferred RFC 2822 style dates with numeric timezones (it used to produce obsolete dates hard coded to "GMT" timezone). An optional 'localtime' flag is added to produce dates in the local timezone, with daylight savings time properly taken into account.
  • In pickle and cPickle, instead of masking errors in load() by transforming them into SystemError, we let the original exception propagate out. Also, implement support for __safe_for_unpickling__ in pickle, as it already was supported in cPickle.



  • The dbm module is built using libdb1 if available. The bsddb module is built with libdb3 if available.
  • Misc/ has been removed by BDFL pronouncement.


  • New function PySequence_Fast_GET_SIZE() returns the size of a non- NULL result from PySequence_Fast(), more quickly than calling PySequence_Size().
  • New argument unpacking function PyArg_UnpackTuple() added.
  • New functions PyObject_CallFunctionObjArgs() and PyObject_CallMethodObjArgs() have been added to make it more convenient and efficient to call functions and methods from C.
  • PyArg_ParseTupleAndKeywords() no longer masks errors, so it's possible that this will propagate errors it didn't before.
  • New function PyObject_CheckReadBuffer(), which returns true if its argument supports the single-segment readable buffer interface.

New platforms

  • We've finally confirmed that this release builds on HP-UX 11.00, with threads, and passes the test suite.
  • Thanks to a series of patches from Michael Muller, Python may build again under OS/2 Visual Age C++.
  • Updated RISCOS port by Dietmar Schwertberger.


  • Added a test script for the curses module. It isn't run automatically; must be run with '-u curses' to enable it.



  • PythonScript has been moved to unsupported and is slated to be removed completely in the next release.
  • It should now be possible to build applets that work on both OS9 and OSX.
  • The core is now linked with CoreServices not Carbon; as a side result, default 8bit encoding on OSX is now ASCII.
  • Python should now build on OSX 10.1.1

What's New in Python 2.2b1?

Release date: 19-Oct-2001

Type/class unification and new-style classes

  • New-style classes are now always dynamic (except for built-in and extension types). There is no longer a performance penalty, and I no longer see another reason to keep this baggage around. One relic remains: the __dict__ of a new-style class is a read-only proxy; you must set the class's attribute to modify it. As a consequence, the __defined__ attribute of new-style types no longer exists, for lack of need: there is once again only one __dict__ (although in the future a __cache__ may be resurrected with a similar function, if I can prove that it actually speeds things up).
  • C.__doc__ now works as expected for new-style classes (in 2.2a4 it always returned None, even when there was a class docstring).
  • doctest now finds and runs docstrings attached to new-style classes, class methods, static methods, and properties.

Core and builtins

  • A very subtle syntactical pitfall in list comprehensions was fixed. For example: [a+b for a in 'abc', for b in 'def']. The comma in this example is a mistake. Previously, this would silently let 'a' iterate over the singleton tuple ('abc',), yielding ['abcd', 'abce', 'abcf'] rather than the intended ['ad', 'ae', 'af', 'bd', 'be', 'bf', 'cd', 'ce', 'cf']. Now, this is flagged as a syntax error. Note that [a for a in <singleton>] is a convoluted way to say [<singleton>] anyway, so it's not like any expressiveness is lost.

  • getattr(obj, name, default) now only catches AttributeError, as documented, rather than returning the default value for all exceptions (which could mask bugs in a __getattr__ hook, for example).

  • Weak reference objects are now part of the core and offer a C API. A bug which could allow a core dump when binary operations involved proxy reference has been fixed. weakref.ReferenceError is now a built-in exception.

  • unicode(obj) now behaves more like str(obj), accepting arbitrary objects, and calling a __unicode__ method if it exists. unicode(obj, encoding) and unicode(obj, encoding, errors) still require an 8-bit string or character buffer argument.

  • isinstance() now allows any object as the first argument and a class, a type or something with a __bases__ tuple attribute for the second argument. The second argument may also be a tuple of a class, type, or something with __bases__, in which case isinstance() will return true if the first argument is an instance of any of the things contained in the second argument tuple. E.g.

    isinstance(x, (A, B))

    returns true if x is an instance of A or B.

Extension modules

  • thread.start_new_thread() now returns the thread ID (previously None).
  • binascii has now two quopri support functions, a2b_qp and b2a_qp.
  • readline now supports setting the startup_hook and the pre_event_hook, and adds the add_history() function.
  • os and posix supports chroot(), setgroups() and unsetenv() where available. The stat(), fstat(), statvfs() and fstatvfs() functions now return "pseudo-sequences" -- the various fields can now be accessed as attributes (e.g. os.stat("/").st_mtime) but for backwards compatibility they also behave as a fixed-length sequence. Some platform-specific fields (e.g. st_rdev) are only accessible as attributes.
  • time: localtime(), gmtime() and strptime() now return a pseudo-sequence similar to the os.stat() return value, with attributes like tm_year etc.
  • Decompression objects in the zlib module now accept an optional second parameter to decompress() that specifies the maximum amount of memory to use for the uncompressed data.
  • optional SSL support in the socket module now exports OpenSSL functions RAND_add(), RAND_egd(), and RAND_status(). These calls are useful on platforms like Solaris where OpenSSL does not automatically seed its PRNG. Also, the keyfile and certfile arguments to socket.ssl() are now optional.
  • posixmodule (and by extension, the os module on POSIX platforms) now exports O_LARGEFILE, O_DIRECT, O_DIRECTORY, and O_NOFOLLOW.


  • doctest now excludes functions and classes not defined by the module being tested, thanks to Tim Hochberg.

  • HotShot, a new profiler implemented using a C-based callback, has been added. This substantially reduces the overhead of profiling, but it is still quite preliminary. Support modules and documentation will be added in upcoming releases (before 2.2 final).

  • profile now produces correct output in situations where an exception raised in Python is cleared by C code (e.g. hasattr()). This used to cause wrong output, including spurious claims of recursive functions and attribution of time spent to the wrong function.

    The code and documentation for the derived OldProfile and HotProfile profiling classes was removed. The code hasn't worked for years (if you tried to use them, they raised exceptions). OldProfile intended to reproduce the behavior of the profiler Python used more than 7 years ago, and isn't interesting anymore. HotProfile intended to provide a faster profiler (but producing less information), and that's a worthy goal we intend to meet via a different approach (but without losing information).

  • Profile.calibrate() has a new implementation that should deliver a much better system-specific calibration constant. The constant can now be specified in an instance constructor, or as a Profile class or instance variable, instead of by editing's source code. Calibration must still be done manually (see the docs for the profile module).

    Note that Profile.calibrate() must be overridden by subclasses. Improving the accuracy required exploiting detailed knowledge of profiler internals; the earlier method abstracted away the details and measured a simplified model instead, but consequently computed a constant too small by a factor of 2 on some modern machines.

  • quopri's encode and decode methods take an optional header parameter, which indicates whether output is intended for the header 'Q' encoding.

  • The SocketServer.ThreadingMixIn class now closes the request after finish_request() returns. (Not when it errors out though.)

  • The nntplib module's NNTP.body() method has grown a 'file' argument to allow saving the message body to a file.

  • The email package has added a class email.Parser.HeaderParser which only parses headers and does not recurse into the message's body. Also, the module/class MIMEAudio has been added for representing audio data (contributed by Anthony Baxter).

  • ftplib should be able to handle files > 2GB.

  • ConfigParser.getboolean() now also interprets TRUE, FALSE, YES, NO, ON, and OFF.

  • xml.dom.minidom NodeList objects now support the length attribute and item() method as required by the DOM specifications.


  • Demo/dns was removed. It no longer serves any purpose; a package derived from it is now maintained by Anthony Baxter, see
  • The freeze tool has been made more robust, and two new options have been added: -X and -E.


  • configure will use CXX in LINKCC if CXX is used to build main() and the system requires to link a C++ main using the C++ compiler.


  • The documentation for the tp_compare slot is updated to require that the return value must be -1, 0, 1; an arbitrary number <0 or >0 is not correct. This is not yet enforced but will be enforced in Python 2.3; even later, we may use -2 to indicate errors and +2 for "NotImplemented". Right now, -1 should be used for an error return.
  • PyLong_AsLongLong() now accepts int (as well as long) arguments. Consequently, PyArg_ParseTuple's 'L' code also accepts int (as well as long) arguments.
  • PyThread_start_new_thread() now returns a long int giving the thread ID, if one can be calculated; it returns -1 for error, 0 if no thread ID is calculated (this is an incompatible change, but only the thread module used this API). This code has only really been tested on Linux and Windows; other platforms please beware (and report any bugs or strange behavior).
  • PyUnicode_FromEncodedObject() no longer accepts Unicode objects as input.

New platforms



  • Installer: If you install IDLE, and don't disable file-extension registration, a new "Edit with IDLE" context (right-click) menu entry is created for .py and .pyw files.

  • The signal module now supports SIGBREAK on Windows, thanks to Steven Scott. Note that SIGBREAK is unique to Windows. The default SIGBREAK action remains to call Win32 ExitProcess(). This can be changed via signal.signal(). For example:

    # Make Ctrl+Break raise KeyboardInterrupt, like Python's default Ctrl+C
    # (SIGINT) behavior.
    import signal
    signal.signal(signal.SIGBREAK, signal.default_int_handler)
        while 1:
    except KeyboardInterrupt:
        # We get here on Ctrl+C or Ctrl+Break now; if we had not changed
        # SIGBREAK, only on Ctrl+C (and Ctrl+Break would terminate the
        # program without the possibility for any Python-level cleanup).
        print "Clean exit"

What's New in Python 2.2a4?

Release date: 28-Sep-2001

Type/class unification and new-style classes

  • pydoc and inspect are now aware of new-style classes; e.g. help(list) at the interactive prompt now shows proper documentation for all operations on list objects.
  • Applications using Jim Fulton's ExtensionClass module can now safely be used with Python 2.2. In particular, Zope 2.4.1 now works with Python 2.2 (as well as with Python 2.1.1). The Demo/metaclass examples also work again. It is hoped that Gtk and Boost also work with 2.2a4 and beyond. (If you can confirm this, please write; if there are still problems, please open a bug report on SourceForge.)
  • property() now takes 4 keyword arguments: fget, fset, fdel and doc. These map to read-only attributes 'fget', 'fset', 'fdel', and '__doc__' in the constructed property object. fget, fset and fdel weren't discoverable from Python in 2.2a3. __doc__ is new, and allows to associate a docstring with a property.
  • Comparison overloading is now more completely implemented. For example, a str subclass instance can properly be compared to a str instance, and it can properly overload comparison. Ditto for most other built-in object types.
  • The repr() of new-style classes has changed; instead of <type 'M.Foo'> a new-style class is now rendered as <class 'M.Foo'>, except for built-in types, which are still rendered as <type 'Foo'> (to avoid upsetting existing code that might parse or otherwise rely on repr() of certain type objects).
  • The repr() of new-style objects is now always <Foo object at XXX>; previously, it was sometimes <Foo instance at XXX>.
  • For new-style classes, what was previously called __getattr__ is now called __getattribute__. This method, if defined, is called for every attribute access. A new __getattr__ hook more similar to the one in classic classes is defined which is called only if regular attribute access raises AttributeError; to catch all attribute access, you can use __getattribute__ (for new-style classes). If both are defined, __getattribute__ is called first, and if it raises AttributeError, __getattr__ is called.
  • The __class__ attribute of new-style objects can be assigned to. The new class must have the same C-level object layout as the old class.
  • The builtin file type can be subclassed now. In the usual pattern, "file" is the name of the builtin type, and file() is a new builtin constructor, with the same signature as the builtin open() function. file() is now the preferred way to open a file.
  • Previously, __new__ would only see sequential arguments passed to the type in a constructor call; __init__ would see both sequential and keyword arguments. This made no sense whatsoever any more, so now both __new__ and __init__ see all arguments.
  • Previously, hash() applied to an instance of a subclass of str or unicode always returned 0. This has been repaired.
  • Previously, an operation on an instance of a subclass of an immutable type (int, long, float, complex, tuple, str, unicode), where the subtype didn't override the operation (and so the operation was handled by the builtin type), could return that instance instead a value of the base type. For example, if s was of a str subclass type, s[:] returned s as-is. Now it returns a str with the same value as s.
  • Provisional support for pickling new-style objects has been added.


  • file.writelines() now accepts any iterable object producing strings.
  • PyUnicode_FromEncodedObject() now works very much like PyObject_Str(obj) in that it tries to use __str__/tp_str on the object if the object is not a string or buffer. This makes unicode() behave like str() when applied to non-string/buffer objects.
  • PyFile_WriteObject now passes Unicode objects to the file's write method. As a result, all file-like objects which may be the target of a print statement must support Unicode objects, i.e. they must at least convert them into ASCII strings.
  • Thread scheduling on Solaris should be improved; it is no longer necessary to insert a small sleep at the start of a thread in order to let other runnable threads be scheduled.


  • StringIO.StringIO instances and cStringIO.StringIO instances support read character buffer compatible objects for their .write() methods. These objects are converted to strings and then handled as such by the instances.
  • The "email" package has been added. This is basically a port of the mimelib package <> with API changes and some implementations updated to use iterators and generators.
  • difflib.ndiff() and are generators now. This restores the ability of Tools/scripts/ to start producing output before the entire comparison is complete.
  • StringIO.StringIO instances and cStringIO.StringIO instances support iteration just like file objects (i.e. their .readline() method is called for each iteration until it returns an empty string).
  • The codecs module has grown four new helper APIs to access builtin codecs: getencoder(), getdecoder(), getreader(), getwriter().
  • SimpleXMLRPCServer: a new module (based upon SimpleHTMLServer) simplifies writing XML RPC servers.
  • os.path.realpath(): a new function that returns the absolute pathname after interpretation of symbolic links. On non-Unix systems, this is an alias for os.path.abspath().
  • operator.indexOf() (PySequence_Index() in the C API) now works with any iterable object.
  • smtplib now supports various authentication and security features of the SMTP protocol through the new login() and starttls() methods.
  • hmac: a new module implementing keyed hashing for message authentication.
  • mimetypes now recognizes more extensions and file types. At the same time, some mappings not sanctioned by IANA were removed.
  • The "compiler" package has been brought up to date to the state of Python 2.2 bytecode generation. It has also been promoted from a Tool to a standard library package. (Tools/compiler still exists as a sample driver.)


  • Large file support (LFS) is now automatic when the platform supports it; no more manual configuration tweaks are needed. On Linux, at least, it's possible to have a system whose C library supports large files but whose kernel doesn't; in this case, large file support is still enabled but doesn't do you any good unless you upgrade your kernel or share your Python executable with another system whose kernel has large file support.
  • The configure script now supplies plausible defaults in a cross-compilation environment. This doesn't mean that the supplied values are always correct, or that cross-compilation now works flawlessly -- but it's a first step (and it shuts up most of autoconf's warnings about AC_TRY_RUN).
  • The Unix build is now a bit less chatty, courtesy of the parser generator. The build is completely silent (except for errors) when using "make -s", thanks to a -q option to


  • The "structmember" API now supports some new flag bits to deny read and/or write access to attributes in restricted execution mode.

New platforms


  • The "classic" standard tests, which work by comparing stdout to an expected-output file under Lib/test/output/, no longer stop at the first mismatch. Instead the test is run to completion, and a variant of ndiff-style comparison is used to report all differences. This is much easier to understand than the previous style of reporting.
  • The unittest-based standard tests now use regrtest's test_main() convention, instead of running as a side-effect of merely being imported. This allows these tests to be run in more natural and flexible ways as unittests, outside the regrtest framework.
  • is much better integrated with unittest and doctest now, especially in regard to reporting errors.


  • Large file support now also works for files > 4GB, on filesystems that support it (NTFS under Windows 2000). See "What's New in Python 2.2a3" for more detail.

What's New in Python 2.2a3?

Release Date: 07-Sep-2001


  • Conversion of long to float now raises OverflowError if the long is too big to represent as a C double.

  • The 3-argument builtin pow() no longer allows a third non-None argument if either of the first two arguments is a float, or if both are of integer types and the second argument is negative (in which latter case the arguments are converted to float, so this is really the same restriction).

  • The builtin dir() now returns more information, and sometimes much more, generally naming all attributes of an object, and all attributes reachable from the object via its class, and from its class's base classes, and so on from them too. Example: in 2.2a2, dir([]) returned an empty list. In 2.2a3,

    >>> dir([])
    ['__add__', '__class__', '__contains__', '__delattr__', '__delitem__',
     '__eq__', '__ge__', '__getattr__', '__getitem__', '__getslice__',
     '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__le__',
     '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__repr__',
     '__rmul__', '__setattr__', '__setitem__', '__setslice__', '__str__',
     'append', 'count', 'extend', 'index', 'insert', 'pop', 'remove',
     'reverse', 'sort']

    dir(module) continues to return only the module's attributes, though.

  • Overflowing operations on plain ints now return a long int rather than raising OverflowError. This is a partial implementation of PEP 237. You can use -Wdefault::OverflowWarning to enable a warning for this situation, and -Werror::OverflowWarning to revert to the old OverflowError exception.

  • A new command line option, -Q<arg>, is added to control run-time warnings for the use of classic division. (See PEP 238.) Possible values are -Qold, -Qwarn, -Qwarnall, and -Qnew. The default is -Qold, meaning the / operator has its classic meaning and no warnings are issued. Using -Qwarn issues a run-time warning about all uses of classic division for int and long arguments; -Qwarnall also warns about classic division for float and complex arguments (for use with [Note: the remainder of this item (preserved below) became obsolete in 2.2c1 -- -Qnew has global effect in 2.2]

    Using -Qnew is questionable; it turns on new division by default, but
    only in the __main__ module.  You can usefully combine -Qwarn or
    -Qwarnall and -Qnew: this gives the __main__ module new division, and
    warns about classic division everywhere else.
  • Many built-in types can now be subclassed. This applies to int, long, float, str, unicode, and tuple. (The types complex, list and dictionary can also be subclassed; this was introduced earlier.) Note that restrictions apply when subclassing immutable built-in types: you can only affect the value of the instance by overloading __new__. You can add mutable attributes, and the subclass instances will have a __dict__ attribute, but you cannot change the "value" (as implemented by the base class) of an immutable subclass instance once it is created.

  • The dictionary constructor now takes an optional argument, a mapping-like object, and initializes the dictionary from its (key, value) pairs.

  • A new built-in type, super, has been added. This facilitates making "cooperative super calls" in a multiple inheritance setting. For an explanation, see

  • A new built-in type, property, has been added. This enables the creation of "properties". These are attributes implemented by getter and setter functions (or only one of these for read-only or write-only attributes), without the need to override __getattr__. See

  • The syntax of floating-point and imaginary literals has been liberalized, to allow leading zeroes. Examples of literals now legal that were SyntaxErrors before:

    00.0 0e3 0100j 07.5 00000000000000000008.

  • An old tokenizer bug allowed floating point literals with an incomplete exponent, such as 1e and 3.1e-. Such literals now raise SyntaxError.


  • telnetlib includes symbolic names for the options, and support for setting an option negotiation callback. It also supports processing of suboptions.
  • The new C standard no longer requires that math libraries set errno to ERANGE on overflow. For platform libraries that exploit this new freedom, Python's overflow-checking was wholly broken. A new overflow- checking scheme attempts to repair that, but may not be reliable on all platforms (C doesn't seem to provide anything both useful and portable in this area anymore).
  • Asynchronous timeout actions are available through the new class threading.Timer.
  • math.log and math.log10 now return sensible results for even huge long arguments. For example, math.log10(10 ** 10000) ~= 10000.0.
  • A new function, imp.lock_held(), returns 1 when the import lock is currently held. See the docs for the imp module.
  • pickle, cPickle and marshal on 32-bit platforms can now correctly read dumps containing ints written on platforms where Python ints are 8 bytes. When read on a box where Python ints are 4 bytes, such values are converted to Python longs.
  • In restricted execution mode (using the rexec module), unmarshalling code objects is no longer allowed. This plugs a security hole.
  • unittest.TestResult instances no longer store references to tracebacks generated by test failures. This prevents unexpected dangling references to objects that should be garbage collected between tests.


  • Tools/scripts/ has been added which can be used to fix division operators as per PEP 238.


  • If you are an adventurous person using Mac OS X you may want to look at Mac/OSX. There is a Makefile there that will build Python as a real Mac application, which can be used for experimenting with Carbon or Cocoa. Discussion of this on pythonmac-sig, please.


  • New function PyObject_Dir(obj), like Python __builtin__.dir(obj).

  • Note that PyLong_AsDouble can fail! This has always been true, but no callers checked for it. It's more likely to fail now, because overflow errors are properly detected now. The proper way to check:

    double x = PyLong_AsDouble(some_long_object);
    if (x == -1.0 && PyErr_Occurred()) {
            /* The conversion failed. */
  • The GC API has been changed. Extensions that use the old API will still compile but will not participate in GC. To upgrade an extension module:

    • use PyObject_GC_New or PyObject_GC_NewVar to allocate objects and PyObject_GC_Del to deallocate them
    • rename PyObject_GC_Init to PyObject_GC_Track and PyObject_GC_Fini to PyObject_GC_UnTrack
    • remove PyGC_HEAD_SIZE from object size calculations
    • remove calls to PyObject_AS_GC and PyObject_FROM_GC
  • Two new functions: PyString_FromFormat() and PyString_FromFormatV(). These can be used safely to construct string objects from a sprintf-style format string (similar to the format string supported by PyErr_Format()).

New platforms

  • Stephen Hansen contributed patches sufficient to get a clean compile under Borland C (Windows), but he reports problems running it and ran out of time to complete the port. Volunteers? Expect a MemoryError when importing the types module; this is probably shallow, and causing later failures too.



  • Large file support is now enabled on Win32 platforms as well as on Win64. This means that, for example, you can use f.tell() and to manipulate files larger than 2 gigabytes (provided you have enough disk space, and are using a Windows filesystem that supports large partitions). Windows filesystem limits: FAT has a 2GB (gigabyte) filesize limit, and large file support makes no difference there. FAT32's limit is 4GB, and files >= 2GB are easier to use from Python now. NTFS has no practical limit on file size, and files of any size can be used from Python now.
  • The w9xpopen hack is now used on Windows NT and 2000 too when COMPSPEC points to (patch from Brian Quinlan).

What's New in Python 2.2a2?

Release Date: 22-Aug-2001


  • Tim Peters developed a brand new Windows installer using Wise 8.1, generously donated to us by Wise Solutions.
  • configure supports a new option --enable-unicode, with the values ucs2 and ucs4 (new in 2.2a1). With --disable-unicode, the Unicode type and supporting code is completely removed from the interpreter.
  • A new configure option --enable-framework builds a Mac OS X framework, which "make frameworkinstall" will install. This provides a starting point for more mac-like functionality, join if you are interested in helping.
  • The NeXT platform is no longer supported.
  • The 'new' module is now statically linked.


  • The new Tools/scripts/ can be used to automatically edit out obsolete future statements from Python source code. See the module docstring for details.


  • now knows which tests are expected to be skipped on some platforms, allowing to give clearer test result output. regrtest also has optional --use/-u switch to run normally disabled tests which require network access or consume significant disk resources.
  • Several new tests in the standard test suite, with special thanks to Nick Mathewson.


  • The floor division operator // has been added as outlined in PEP 238. The / operator still provides classic division (and will until Python 3.0) unless "from __future__ import division" is included, in which case the / operator will provide true division. The operator module provides truediv() and floordiv() functions. Augmented assignment variants are included, as are the equivalent overloadable methods and C API methods. See the PEP for a full discussion: <>
  • Future statements are now effective in simulated interactive shells (like IDLE). This should "just work" by magic, but read Michael Hudson's "Future statements in simulated shells" PEP 264 for full details: <>.
  • The type/class unification (PEP 252-253) was integrated into the trunk and is not so tentative any more (the exact specification of some features is still tentative). A lot of work has done on fixing bugs and adding robustness and features (performance still has to come a long way).
  • Warnings about a mismatch in the Python API during extension import now use the Python warning framework (which makes it possible to write filters for these warnings).
  • A function's __dict__ (aka func_dict) will now always be a dictionary. It used to be possible to delete it or set it to None, but now both actions raise TypeErrors. It is still legal to set it to a dictionary object. Getting func.__dict__ before any attributes have been assigned now returns an empty dictionary instead of None.
  • A new command line option, -E, was added which disables the use of all environment variables, or at least those that are specifically significant to Python. Usually those have a name starting with "PYTHON". This was used to fix a problem where the tests fail if the user happens to have PYTHONHOME or PYTHONPATH pointing to an older distribution.


  • New class Differ and new functions ndiff() and restore() in These package the algorithms used by the popular Tools/scripts/, for programmatic reuse.
  • New function xml.sax.saxutils.quoteattr(): Quote an XML attribute value using the minimal quoting required for the value; more reliable than using xml.sax.saxutils.escape() for attribute values.
  • Readline completion support for cmd.Cmd was added.
  • Calling os.tempnam() or os.tmpnam() generate RuntimeWarnings.
  • Added function threading.BoundedSemaphore()
  • Added Ka-Ping Yee's module.
  • The 'new' module now exposes the CO_xxx flags.
  • The gc module offers the get_referents function.

New platforms


  • Two new APIs PyOS_snprintf() and PyOS_vsnprintf() were added which provide a cross-platform implementations for the relatively new snprintf()/vsnprintf() C lib APIs. In contrast to the standard sprintf() and vsprintf() C lib APIs, these versions apply bounds checking on the used buffer which enhances protection against buffer overruns.
  • Unicode APIs now use name mangling to assure that mixing interpreters and extensions using different Unicode widths is rendered next to impossible. Trying to import an incompatible Unicode-aware extension will result in an ImportError. Unicode extensions writers must make sure to check the Unicode width compatibility in their extensions by using at least one of the mangled Unicode APIs in the extension.
  • Two new flags METH_NOARGS and METH_O are available in method definition tables to simplify implementation of methods with no arguments and a single untyped argument. Calling such methods is more efficient than calling corresponding METH_VARARGS methods. METH_OLDARGS is now deprecated.


  • "import module" now compiles module.pyw if it exists and nothing else relevant is found.

What's New in Python 2.2a1?

Release date: 18-Jul-2001


  • TENTATIVELY, a large amount of code implementing much of what's described in PEP 252 (Making Types Look More Like Classes) and PEP 253 (Subtyping Built-in Types) was added. This will be released with Python 2.2a1. Documentation will be provided separately through The purpose of releasing this with Python 2.2a1 is to test backwards compatibility. It is possible, though not likely, that a decision is made not to release this code as part of 2.2 final, if any serious backwards incompatibilities are found during alpha testing that cannot be repaired.

  • Generators were added; this is a new way to create an iterator (see below) using what looks like a simple function containing one or more 'yield' statements. See PEP 255. Since this adds a new keyword to the language, this feature must be enabled by including a future statement: "from __future__ import generators" (see PEP 236). Generators will become a standard feature in a future release (probably 2.3). Without this future statement, 'yield' remains an ordinary identifier, but a warning is issued each time it is used. (These warnings currently don't conform to the warnings framework of PEP 230; we intend to fix this in 2.2a2.)

  • The UTF-16 codec was modified to be more RFC compliant. It will now only remove BOM characters at the start of the string and then only if running in native mode (UTF-16-LE and -BE won't remove a leading BMO character).

  • Strings now have a new method .decode() to complement the already existing .encode() method. These two methods provide direct access to the corresponding decoders and encoders of the registered codecs.

    To enhance the usability of the .encode() method, the special casing of Unicode object return values was dropped (Unicode objects were auto-magically converted to string using the default encoding).

    Both methods will now return whatever the codec in charge of the requested encoding returns as object, e.g. Unicode codecs will return Unicode objects when decoding is requested ("הצ".decode("latin-1") will return u"הצ"). This enables codec writer to create codecs for various simple to use conversions.

    New codecs were added to demonstrate these new features (the .encode() and .decode() columns indicate the type of the returned objects):

    Name .encode() .decode() Description
    uu string string UU codec (e.g. for email)
    base64 string string base64 codec
    quopri string string quoted-printable codec
    zlib string string zlib compression
    hex string string 2-byte hex codec
    rot-13 string Unicode ROT-13 Unicode charmap codec
  • Some operating systems now support the concept of a default Unicode encoding for file system operations. Notably, Windows supports 'mbcs' as the default. The Macintosh will also adopt this concept in the medium term, although the default encoding for that platform will be other than 'mbcs'.

    On operating system that support non-ASCII filenames, it is common for functions that return filenames (such as os.listdir()) to return Python string objects pre-encoded using the default file system encoding for the platform. As this encoding is likely to be different from Python's default encoding, converting this name to a Unicode object before passing it back to the Operating System would result in a Unicode error, as Python would attempt to use its default encoding (generally ASCII) rather than the default encoding for the file system.

    In general, this change simply removes surprises when working with Unicode and the file system, making these operations work as you expect, increasing the transparency of Unicode objects in this context. See [????] for more details, including examples.

  • Float (and complex) literals in source code were evaluated to full precision only when running from a .py file; the same code loaded from a .pyc (or .pyo) file could suffer numeric differences starting at about the 12th significant decimal digit. For example, on a machine with IEEE-754 floating arithmetic,

    x = 9007199254740992.0 print long(x)

    printed 9007199254740992 if run directly from .py, but 9007199254740000 if from a compiled (.pyc or .pyo) file. This was due to marshal using str(float) instead of repr(float) when building code objects. marshal now uses repr(float) instead, which should reproduce floats to full machine precision (assuming the platform C float<->string I/O conversion functions are of good quality).

    This may cause floating-point results to change in some cases, and usually for the better, but may also cause numerically unstable algorithms to break.

  • The implementation of dicts suffers fewer collisions, which has speed benefits. However, the order in which dict entries appear in dict.keys(), dict.values() and dict.items() may differ from previous releases for a given dict. Nothing is defined about this order, so no program should rely on it. Nevertheless, it's easy to write test cases that rely on the order by accident, typically because of printing the str() or repr() of a dict to an "expected results" file. See Lib/test/'s new sortdict(dict) function for a simple way to display a dict in sorted order.

  • Many other small changes to dicts were made, resulting in faster operation along the most common code paths.

  • Dictionary objects now support the "in" operator: "x in dict" means the same as dict.has_key(x).

  • The update() method of dictionaries now accepts generic mapping objects. Specifically the argument object must support the .keys() and __getitem__() methods. This allows you to say, for example, {}.update(UserDict())

  • Iterators were added; this is a generalized way of providing values to a for loop. See PEP 234. There's a new built-in function iter() to return an iterator. There's a new protocol to get the next value from an iterator using the next() method (in Python) or the tp_iternext slot (in C). There's a new protocol to get iterators using the __iter__() method (in Python) or the tp_iter slot (in C). Iterating (i.e. a for loop) over a dictionary generates its keys. Iterating over a file generates its lines.

  • The following functions were generalized to work nicely with iterator arguments:

    map(), filter(), reduce(), zip()
    list(), tuple() (PySequence_Tuple() and PySequence_Fast() in C API)
    max(), min()
    join() method of strings
    extend() method of lists
    'x in y' and 'x not in y' (PySequence_Contains() in C API)
    operator.countOf() (PySequence_Count() in C API)
    right-hand side of assignment statements with multiple targets, such as ::
        x, y, z = some_iterable_object_returning_exactly_3_values
  • Accessing module attributes is significantly faster (for example, random.random or os.path or yourPythonModule.yourAttribute).

  • Comparing dictionary objects via == and != is faster, and now works even if the keys and values don't support comparisons other than ==.

  • Comparing dictionaries in ways other than == and != is slower: there were insecurities in the dict comparison implementation that could cause Python to crash if the element comparison routines for the dict keys and/or values mutated the dicts. Making the code bulletproof slowed it down.

  • Collisions in dicts are resolved via a new approach, which can help dramatically in bad cases. For example, looking up every key in a dict d with d.keys() == [i << 16 for i in range(20000)] is approximately 500x faster now. Thanks to Christian Tismer for pointing out the cause and the nature of an effective cure (last December! better late than never).

  • repr() is much faster for large containers (dict, list, tuple).


  • The constants ascii_letters, ascii_lowercase. and ascii_uppercase were added to the string module. These a locale-independent constants, unlike letters, lowercase, and uppercase. These are now use in appropriate locations in the standard library.
  • The flags used in dlopen calls can now be configured using sys.setdlopenflags and queried using sys.getdlopenflags.
  • Fredrik Lundh's xmlrpclib is now a standard library module. This provides full client-side XML-RPC support. In addition, Demo/xmlrpc/ contains two server frameworks (one SocketServer-based, one asyncore-based). Thanks to Eric Raymond for the documentation.
  • The xrange() object is simplified: it no longer supports slicing, repetition, comparisons, efficient 'in' checking, the tolist() method, or the start, stop and step attributes. See PEP 260.
  • A new function fnmatch.filter to filter lists of file names was added.
  • uses month and day names based on the current locale.
  • strop is now really obsolete (this was announced before with 1.6), and issues DeprecationWarning when used (except for the four items that are still imported into
  • now sorts key+value pairs by key in output strings.
  • pprint.isrecursive(object) didn't correctly identify recursive objects. Now it does.
  • pprint functions now much faster for large containers (tuple, list, dict).
  • New 'q' and 'Q' format codes in the struct module, corresponding to C types "long long" and "unsigned long long" (on Windows, __int64). In native mode, these can be used only when the platform C compiler supports these types (when HAVE_LONG_LONG is #define'd by the Python config process), and then they inherit the sizes and alignments of the C types. In standard mode, 'q' and 'Q' are supported on all platforms, and are 8-byte integral types.
  • The site module installs a new built-in function 'help' that invokes It must be invoked as 'help()'; when invoked as 'help', it displays a message reminding the user to use 'help()' or 'help(object)'.


  • New runs dict comparisons where the key and value comparison operators mutate the dicts randomly during comparison. This rapidly causes Python to crash under earlier releases (not for the faint of heart: it can also cause Win9x to freeze or reboot!).
  • New verifies that pprint.isrecursive() and pprint.isreadable() return sensible results. Also verifies that simple cases produce correct output.


  • Removed the unused last_is_sticky argument from the internal _PyTuple_Resize(). If this affects you, you were cheating.

(For information about older versions, consult the HISTORY file.)

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