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...declaration. Even though some editors (like IDLE and Emacs) support the declarations of PEP 263, many editors still do not (and never will); users have to explicitly adjust the encoding which the editor assumes on a file-by-file basis. When the default encoding is changed to UTF-8, adding non-ASCII text to Python files becomes easier and more portable: On some systems, editors will automatically choose UTF-8 when saving text (e.g. on Unix systems where the locale uses UTF-8). On other systems, e...
...declaration rules create confusion when type aliases involve forward references, invalid types, or violate other restrictions enforced on type alias declaration. Because the distinction between an unannotated value and a type alias is implicit, ambiguous or incorrect type alias declarations implicitly default to a valid value assignment. This creates expressions that are impossible to express as type aliases and punts error diagnosis of malformed type aliases downstream. The following examples e...
...declarations PEP:3117 Title:Postfix type declarations Author:Georg Brandl <georg at python.org> Status:Rejected Type:Standards Track Created:01-Apr-2007 Python-Version:3.0 Post-History: Contents Abstract Rationale Specification Unicode replacement units The typedef statement Example Compatibility issues Rejection References Acknowledgements Copyright Abstract This PEP proposes the addition of a postfix type declaration syntax to Python. It also specifies a new typedef...
...declarations may be placed into .c files. Duplicate declarations are allowed as long as the function types are identical. It is encouraged to declare custom converter types a second time right above the converter function definition. The preprocessor will then catch any mismatch between the declarations. In order to keep the converter complexity manageable, PY_SSIZE_T_CLEAN will be deprecated and Py_ssize_t will be assumed for all length arguments. TBD: Make a list of fantasy types like rw_buffe...
PEP 4 -- Deprecation of Standard Modules PEP:4 Title:Deprecation of Standard Modules Author:Brett Cannon <brett at python.org>, Martin von Löwis <martin at v.loewis.de> Status:Active Type:Process Created:01-Oct-2000 Post-History: Contents Introduction Procedure for declaring a module deprecated For modules existing in both Python 2.7 and Python 3.5 Procedure for declaring a module undeprecated Obsolete modules Deprecated modules Deprecation of modules removed in P...
...declarations) intermingled declarations booleans C++-style line comments Python versions before 3.6 used ANSI/ISO standard C (the 1989 version of the standard). This meant (amongst many other things) that all declarations must be at the top of a block (not necessarily at the top of function). Don't use compiler-specific extensions, such as those of GCC or MSVC (e.g. don't write multi-line strings without trailing backslashes). All function declarations and definitions must use full prototypes...
...declaration of C structs; COM objects; Automatic translation of Python classes into IDL or database schemas, such as used in an ORM; and so on. In such cases, it would be useful for a Python programmer to specify such ordering directly using the declaration order of class members. Currently, such orderings must be specified explicitly, using some other mechanism (see the ctypes module for an example.) Unfortunately, the current method for declaring a metaclass does not allow for this, since the ...
...declaration as a declaration of "iso-8859-1". This will cause arbitrary byte strings to correctly round-trip between step 2 and step 5 of the processing, and provide compatibility with Python 2.2 for Unicode literals that contain non-ASCII bytes. A warning will be issued if non-ASCII bytes are found in the input, once per improperly encoded input file. Remove the warning, and change the default encoding to "ascii". The builtin compile() API will be enhanced to accept Unicode as input. 8-bit ...
...declaration [2] in the source file. The Unicode-specific escape sequences \uxxxx, \Uxxxxxxxx, and \N{name} are unrecognized in Python 2.x and forbidden in Python 3000. Adjacent bytes literals are subject to the same concatenation rules as adjacent string literals [3]. A bytes literal adjacent to a string literal is an error. Semantics Each evaluation of a bytes literal produces a new bytes object. The bytes in the new object are the bytes represented by the shortstringitem or longstringitem ...
...declaration per module or class for a given attribute. There can't be separate class-level and instance-level constants with the same name. There must be exactly one assignment to a final name. This means a type checker should prevent further assignments to final names in type-checked code: from typing import Final RATE: Final = 3000 class Base: DEFAULT_ID: Final = 0 RATE = 300 # Error: can't assign to final attribute Base.DEFAULT_ID = 1 # Error: can't override a final attribute Note...
...declaration contracts the scope of an existing name, so inadvertently omitting the declaration could yield farther-reaching (i.e. more dangerous) effects than expected. In Python with this proposal, the extra effort of adding the declaration is aligned with the increased risk of non-local effects (i.e. the path of least resistance is the safer path). Many spellings have been suggested for such a declaration: scoped x [1] global x in f [3] (explicitly specify which scope) free x [5] outer x [6]...
...declaration of a directory as contributing to a package is a desirable property, rather than an obstacle. In particular, Jython developers noticed that Jython could easily mistake a directory that is a Java package as being a Python package, if there is no need to declare Python packages. Packages can stop filling out the namespace package's __init__.py. As a consequence, extend_path and declare_namespace become obsolete. Namespace packages can start providing non-trivial __init__.py implementa...
...declaration to explicitly establish the target name as being local to the function, or else an explicit global or nonlocal declaration. TargetNameError, a new SyntaxError subclass, will be raised at compile time if no such binding or declaration is present. For example, the following code would compile and run as it does today: x = 0 x += 1 # Sets global "x" to 1 class C: x += 1 # Sets local "x" to 2, leaves global "x" alone def local_target(): x = 0 x += 1 # Sets local "x" to 1, ...
...declaration. Indented lines below the function declaration declare parameters, one per line; lines below those that are indented even further are per-parameter docstrings. Finally, the first line dedented back to column 0 end parameter declarations and start the function docstring. Parameter docstrings are optional; function docstrings are not. Functions that specify no arguments may simply specify the function declaration followed by the docstring. Module and Class Declarations When a C fil...
...declaration within parentheses. A version declaration is a series of conditional operators and version numbers, separated by commas. Conditional operators must be one of "<", ">", "<=", ">=", "==", and "!=". Version numbers must be in the format accepted by the distutils.version.StrictVersion class: two or three dot-separated numeric components, with an optional "pre-release" tag on the end consisting of the letter 'a' or 'b' followed by a number. Example version numbers are "1.0"...
...declaration. Function definition: def name ... Argument declaration: def f(...name...), lambda ...name... Class definition: class name ... Assignment statement: name = ... Import statement: import name, import module as name, from module import name Implicit assignment: names are bound by for statements and except clauses There are several cases where Python statements are illegal when used in conjunction with nested scopes that contain free variables. If a variable is referenced in an...
PEP 549 -- Instance Descriptors PEP:549 Title:Instance Descriptors Author:larry at hastings.org (Larry Hastings) Discussions-To:python-dev at python.org Status:Rejected Type:Standards Track Created:04-Sep-2017 Python-Version:3.7 Post-History:04-Sep-2017 Contents Rejection Notice Abstract Rationale Implementation Prototype Acknowledgements References Copyright Rejection Notice https://mail.python.org/pipermail/python-dev/2017-November/150528.html Abstract Python's descr...
...declarations after a post keyword describes exactly what the function or method is allowed to modify. This removes the need for the NoChange syntax in Eiffel, and makes the implementation of __old__ much easier. It also is more in line with Z schemas [9], which are divided into two parts: declaring what changes followed by limiting the changes. Shallow copies of variables for the __old__ value prevent an implementation of contract programming from slowing down a system too much. If a function...
...declaration. A solution to this problem is to move the transformation of the method closer to the method's own declaration. The intent of the new syntax is to replace def foo(cls): pass foo = synchronized(lock)(foo) foo = classmethod(foo) with an alternative that places the decoration in the function's declaration: @classmethod @synchronized(lock) def foo(cls): pass Modifying classes in this fashion is also possible, though the benefits are not as immediately apparent. Almost certa...
...template library. The administrative interface to the site is written using the Quixote Web application framework, and employs mod_scgi behind Apache 2. This interface provides the site administrators access to all of the functions they need to interact with user's profiles, process log files to provide reports about site activity and issues, and update site content. Quixote and mod_scgi have performed extremely well in this application, and plans call for them to replace the current SimpleTAL a...