PEP: 291 Title: Backward Compatibility for Standard Library Version: $Revision$ Last-Modified: $Date$ Author: neal@metaslash.com (Neal Norwitz) Status: Active Type: Informational Created: 06-Jun-2002 Post-History: Python-Version: 2.3 Abstract This PEP describes the packages and modules in the standard library which should remain backward compatible with previous versions of Python. If a package is not listed here, then it need only remain compatible with the version of Python it is distributed with. Rationale Authors have various reasons why packages and modules should continue to work with previous versions of Python. In order to maintain backward compatibility for these modules while moving the rest of the standard library forward, it is necessary to know which modules can be modified and which should use old and possibly deprecated features. Generally, authors should attempt to keep changes backward compatible with the previous released version of Python in order to make bug fixes easier to backport. In addition to a package or module being listed in this PEP, authors must add a comment at the top of each file documenting the compatibility requirement. When a major version of Python is released, a CVS branch is created for continued maintenance and bug fix releases. A package version on a branch may have a different compatibility requirement than the same package on the trunk (i.e. current bleeding-edge development). Where appropriate, these branch compatibilities are listed below. Features to Avoid The following list contains common features to avoid in order to maintain backward compatibility with each version of Python. This list is not complete! It is only meant as a general guide. Note that the features below were implemented in the version following the one listed. For example, features listed next to 1.5.2 were implemented in 2.0. Version Features to Avoid ------- ----------------- 1.5.2 string methods, Unicode, list comprehensions, augmented assignment (eg, +=), zip(), import x as y, dict.setdefault(), print >> f, calling f(*args, **kw), plus all features below 2.0 nested scopes, rich comparisons, function attributes, plus all features below 2.1 use of object or new-style classes, iterators, using generators, nested scopes, or // without from __future__ import ... statement, plus all features below 2.2 bool, True, False, basestring, enumerate(), {}.pop(), PendingDeprecationWarning, Universal Newlines Backward Compatible Packages, Modules, and Tools Package/Module Maintainer(s) Python Version Notes -------------- ------------- -------------- ----- bsddb Greg Smith 2.1 Barry Warsaw compiler Jeremy Hylton 2.1 distutils Andrew Kuchling 1.5.2 email Barry Warsaw 2.1 / 2.3 [1] logging Vinay Sajip 1.5.2 sre Fredrik Lundh 2.1 xml (PyXML) Martin v. Loewis 2.0 xmlrpclib Fredrik Lundh 1.5.2 modulefinder Thomas Heller 2.2 Just van Rossum Tool Maintainer(s) Python Version ---- ------------- -------------- None Notes ----- [1] The email package version 2 was distributed with Python up to Python 2.3, and this must remain Python 2.1 compatible. email package version 3 will be distributed with Python 2.4 and will need to remain compatible only with Python 2.3. Copyright This document has been placed in the public domain. Local Variables: mode: indented-text indent-tabs-mode: nil sentence-end-double-space: t fill-column: 70 End: