142 lines
5.3 KiB
Plaintext
142 lines
5.3 KiB
Plaintext
PEP: 291
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Title: Backward Compatibility for Standard Library
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Version: $Revision$
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Last-Modified: $Date$
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Author: nnorwitz@gmail.com (Neal Norwitz)
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Status: Active
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Type: Informational
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Created: 06-Jun-2002
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Post-History:
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Python-Version: 2.3
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Abstract
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This PEP describes the packages and modules in the standard
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library which should remain backward compatible with previous
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versions of Python. If a package is not listed here, then it need
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only remain compatible with the version of Python it is
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distributed with.
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Rationale
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Authors have various reasons why packages and modules should
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continue to work with previous versions of Python. In order to
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maintain backward compatibility for these modules while moving the
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rest of the standard library forward, it is necessary to know
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which modules can be modified and which should use old and
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possibly deprecated features.
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Generally, authors should attempt to keep changes backward
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compatible with the previous released version of Python in order
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to make bug fixes easier to backport.
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In addition to a package or module being listed in this PEP,
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authors must add a comment at the top of each file documenting
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the compatibility requirement.
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When a major version of Python is released, a Subversion branch is
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created for continued maintenance and bug fix releases. A package
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version on a branch may have a different compatibility requirement
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than the same package on the trunk (i.e. current bleeding-edge
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development). Where appropriate, these branch compatibilities are
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listed below.
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Features to Avoid
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The following list contains common features to avoid in order
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to maintain backward compatibility with each version of Python.
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This list is not complete! It is only meant as a general guide.
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Note that the features below were implemented in the version
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following the one listed. For example, features listed next to
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1.5.2 were implemented in 2.0.
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Version Features to Avoid
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------- -----------------
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1.5.2 string methods, Unicode, list comprehensions,
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augmented assignment (eg, +=), zip(), import x as y,
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dict.setdefault(), print >> f,
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calling f(*args, **kw), plus all features below
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2.0 nested scopes, rich comparisons,
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function attributes, plus all features below
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2.1 use of object or new-style classes, iterators,
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using generators, nested scopes, or //
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without from __future__ import ... statement,
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plus all features below
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2.2 bool, True, False, basestring, enumerate(),
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{}.pop(), PendingDeprecationWarning,
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Universal Newlines, plus all features below
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2.3 generator expressions, multi-line imports,
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decorators, int/long unification, set/frozenset,
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reversed(), sorted(), "".rsplit()
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2.4 ???
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Backward Compatible Packages, Modules, and Tools
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Package/Module Maintainer(s) Python Version Notes
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-------------- ------------- -------------- -----
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bsddb Greg Smith 2.1
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Barry Warsaw
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compiler Jeremy Hylton 2.1
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ctypes Thomas Heller 2.3
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decimal Raymond Hettinger 2.3 [2]
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email Barry Warsaw 2.1 / 2.3 [1]
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logging Vinay Sajip 1.5.2
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modulefinder Thomas Heller 2.2
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Just van Rossum
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pkgutil Phillip Eby 2.3
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platform Marc-Andre Lemburg 1.5.2
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pybench Marc-Andre Lemburg 1.5.2 [3]
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sre Fredrik Lundh 2.1
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subprocess Peter Astrand 2.2
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wsgiref Phillip J. Eby 2.1
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xml (PyXML) Martin v. Loewis 2.0
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xmlrpclib Fredrik Lundh 2.1
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Tool Maintainer(s) Python Version
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---- ------------- --------------
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None
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Notes
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-----
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[1] The email package version 2 was distributed with Python up to
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Python 2.3, and this must remain Python 2.1 compatible. email
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package version 3 will be distributed with Python 2.4 and will
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need to remain compatible only with Python 2.3.
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[2] Specification updates will be treated as bugfixes and backported.
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Python 2.3 compatibility will be kept for at least Python 2.4.
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The decision will be revisited for Python 2.5 and not changed
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unless compelling advantages arise.
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[3] pybench lives under the Tools/ directory. Compatibility with
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older Python versions is needed in order to be able to compare
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performance between Python versions. New features may still
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be used in new tests, which may then be configured to fail
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gracefully on import by the tool in older Python versions.
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Copyright
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This document has been placed in the public domain.
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