Results

• The Python 2.3 Method Resolution Order

  ...pass class F(O): pass class E(O): pass class D(O): pass class C(D,F): pass class B(D,E): pass class A(B,C): pass class ex_6: "My second example" class O: pass class F(O): pass class E(O): pass class D(O): pass class C(D,F): pass class B(E,D): pass class A(B,C): pass class ex_9: "Difference between Python 2.2 MRO and C3" #From Samuele class O: pass class A(O): pass class B(O): pass class C(O): pass ...

• SIG for development of Python/C++ integration

  ...references, in order to prevent dangling pointers and references from causing crashes on the Python side. This limits the library's ability to export arbitrary C++ functions. Goal: Implementation of a mechanism by which references and pointers to internal elements of function and method arguments can be returned safely. This will include a mechanism by which any argument object can be kept alive during the lifetime of any other argument object, so that Wrapped C++ o...

• Unifying types and classes in Python 2.2

  ...by yet another class. Here's an example: class A(object): def meth(self): return "A" class B(object): def meth(self): return "B" class X(A, B): pass class Y(B, A): pass class Z(X, Y): pass If you try this, (using Z.__mro__, see below), you get [Z, X, Y, A, B, object], which does not maintain the monotonicity requirement mentioned above: the MRO for Y is [Y, B, A, object], and this is not a subsequence of the above list! In fact, there is no solution that satisfie...

• Unifying types and classes in Python 2.2

  ...by yet another class. Here's an example: class A(object): def meth(self): return "A" class B(object): def meth(self): return "B" class X(A, B): pass class Y(B, A): pass class Z(X, Y): pass If you try this, (using Z.__mro__, see below), you get [Z, X, Y, A, B, object], which does not maintain the monotonicity requirement mentioned above: the MRO for Y is [Y, B, A, object], and this is not a subsequence of the above list! In fact, there ...

• Unifying types and classes in Python 2.2

  ...by yet another class. Here's an example: class A(object): def meth(self): return "A" class B(object): def meth(self): return "B" class X(A, B): pass class Y(B, A): pass class Z(X, Y): pass If you try this, (using Z.__mro__, see below), you get [Z, X, Y, A, B, object], which does not maintain the monotonicity requirement mentioned above: the MRO for Y is [Y, B, A, object], and this is not a subsequence of the above list! In fact, there ...

• Unifying types and classes in Python 2.2

  ...by yet another class. Here's the smallest example I can think of: class A(object): def meth(self): return "A" class B(object): def meth(self): return "B" class X(A, B): pass class Y(B, A): pass class Z(X, Y): pass According to the algorithm given above, Z's MRO (Method Resolution order) should be [Z, X, Y, B, A, object]. But if you try this in Python 2.2 (using Z.__mro__, see below), you get [Z, X, Y, A, B, object]! In a future vers...

• Metaclasses in Python 1.5

  ...object is never callable. So what do Don and Jim do in order to use Don's hook? Write an extension that defines at least two new Python object types. The first would be the type for ``class-like'' objects usable as a base class, to trigger Don's hook. This type must be made callable. That's why we need a second type. Whether an object is callable depends on its type. So whether a type object is callable depends on its type, which is a meta-type. (In core Python there is only one...

• Debugging Reference Count Problems

  ...reference to them.) Many routines that extract objects from other objects also give you the responsibility of owning a reference to the object, e.g. PyObject_GetAttr() and PyObject_GetItem(). On the other hand (and these are the most common examples, but not the only ones), PyList_GetItem(), PyTuple_GetItem(), PyDict_GetItem() and PyDict_GetItemString() all return to you an object without ownership of a reference to the object. This is called a "borrowed" reference. When you pass a ...

• Python Success Stories

  ...object framework provided by PHP. Memory leaks, inconsistent interfaces, inconsistent internal data model, randomly freed objects, multiple object copies despite explicit use of references, internal PHP errors, and untraceable code failures all but made the task impossible to accomplish in PHP. Even after we achieved a relatively stable code base, we were nowhere near our goal of Core Objects Reused Everywhere because we had to depart from pure object-oriented methods just to work around the pro...

• Highlights: Python 2.5

  ...bytecode. The 'with' operator replaces a common try/finally idiom that results in much cleaner and safer code. Generators gained send, throw and close methods. Values passed to send will be returned by the yield statement when the generator is resumed. throw takes an exception and causes the yield statement to raise the passed exception in the generator. close is used to terminate a generator. This turns generators into a form of coroutine and makes them even more powerful. Conditional expressio...

• Highlights: Python 2.4

  ...passes through the polling loop. The default is still to loop forever. The curses module now supports the ncurses extension use_default_colors(). On platforms where the terminal supports transparency, this makes it possible to use a transparent background. imaplib now supports the IMAP THREAD command heapq has two new functions nlargest() and nsmallest() to find the N largest or smallest values in a dataset. itertools has a new function groupby() that acts a little like an SQL "GROUP BY&quo...

• Notes

  ...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 functio...

• Python 2.4.1 - Release Notes

  ...Object_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_For...

• What's new in Python 2.3

  ...by Gustavo Niemeyer. datetime - a fast, compact implementation in C of date and time calculations ranging from the year 1 to 9999, with optional timezone support; written by Tim Peters. (New in 2.3a2: too much to list here; see Misc/NEWS.) heapq - implements the heap queue algoritm known from 1st year algorithms classes. Code by Kevin O'Connor, write-up by François Pinard, many improvements by Tim Peters. imaplib - added SSL support. imp - exposed the "import lock". (New in 2.3a...

• Notes

  ...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 do...

• Python 2.0

  ...by Barry Warsaw. Described by PEP 214. Optional Collection of Cyclical Garbage Python is now equipped with a garbage collector that can hunt down cyclical references between Python objects. It's no replacement for reference counting; in fact, it depends on the reference counts being correct, and decides that a set of objects belong to a cycle if all their reference counts can be accounted for from their references to each other. This devious scheme was first proposed by Eric Tied...

• Notes

  ...passing compiler variables around. New abstract APIs PyObject_IsInstance(), PyObject_IsSubclass() implement isinstance() and issubclass(). Py_BuildValue() now has a "D" conversion to create a Python complex number from a Py_complex C value. Extensions types which support weak references must now set the field allocated for the weak reference machinery to NULL themselves; this is done to avoid the cost of checking each object for having a weakly referencable type in PyObject_INIT(), sin...

• Standard Exception Classes in Python 1.5

  ...Object *); int PyErr_GivenExceptionMatches(PyObject *, PyObject *); void PyErr_NormalizeException(PyObject**, PyObject**, PyObject**); PyErr_ExceptionMatches(exception) should be used in preference over PyErr_Occurred()==exception, since the latter will return an incorrect result when the exception raised is a class derived from the exception tested for. PyErr_GivenExceptionMatches(raised_exception, exception) performs the same test as PyErr_ExceptionMatches() but allows you to p...

• Python Success Stories

  ...by the aggregation engine, which combines the scores into yearly and monthly blocks, sliced by provider, location, and the number of days into the future for which the forecasts were predicting. In its first year, 2003, the system only gathered forecasts for 20 U.S. cities, or about 250,000 individual forecasts, so most of the data output was based on the raw scoring data. The aggregation engine was added once the system was scaled up to 800 cities, increasing the data stream by almost 4000%. In...

• Python Humor

  ...pass a reference to the gun to a foot object. After the foot is blown up, the gun object remains alive for eternity, ready to shoot all future feet that may happen to appear. Java: You find that Microsoft and Sun have released imcompatible class libraries both implementing Gun objects. You then find that although there are plenty of feet objects implemented in the past in many other languages, you cannot get access to one. But seeing as Java is so cool, you dont care and go around shooting anyth...

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