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PEP:4
Title:Deprecation of Standard Modules
Version:f1fde6ef92e2
Last-Modified:2013-10-18 11:49:14 -0400 (Fri, 18 Oct 2013)
Author:Martin von Löwis <martin at v.loewis.de>
Status:Active
Type:Process
Content-Type:text/x-rst
Created:1-Oct-2000
Post-History:

Introduction

When new modules were added to the standard Python library in the past, it was not possible to foresee whether they would still be useful in the future. Even though Python "Comes With Batteries Included", batteries may discharge over time. Carrying old modules around is a burden on the maintainer, especially when there is no interest in the module anymore.

At the same time, removing a module from the distribution is difficult, as it is not known in general whether anybody is still using it. This PEP defines a procedure for removing modules from the standard Python library. Usage of a module may be 'deprecated', which means that it may be removed from a future Python release. The rationale for deprecating a module is also collected in this PEP. If the rationale turns out faulty, the module may become 'undeprecated'.

Procedure for declaring a module deprecated

Since the status of module deprecation is recorded in this PEP, proposals for deprecating modules MUST be made by providing a change to the text of this PEP, which SHOULD be a patch posted to bugs.python.org.

A proposal for deprecation of the module MUST include the date of the proposed deprecation and a rationale for deprecating it. In addition, the proposal MUST include a change to the documentation of the module; deprecation is indicated by saying that the module is "obsolete" or "deprecated". The proposal SHOULD include a patch for the module's source code to indicate deprecation there as well, by raising a DeprecationWarning. The proposal MUST include patches to remove any use of the deprecated module from the standard library.

It is expected that deprecated modules are included in the Python releases that immediately follows the deprecation; later releases may ship without the deprecated modules.

Procedure for declaring a module undeprecated

When a module becomes deprecated, a rationale is given for its deprecation. In some cases, an alternative interface for the same functionality is provided, so the old interface is deprecated. In other cases, the need for having the functionality of the module may not exist anymore.

If the rationale is faulty, again a change to this PEP's text MUST be submitted. This change MUST include the date of undeprecation and a rationale for undeprecation. Modules that are undeprecated under this procedure MUST be listed in this PEP for at least one major release of Python.

Obsolete modules

A number of modules are already listed as obsolete in the library documentation. These are listed here for completeness.

cl, sv, timing

All these modules have been declared as obsolete in Python 2.0, some even earlier.

The following obsolete modules were removed in Python 2.5:

addpack, cmp, cmpcache, codehack, dircmp, dump, find, fmt, grep, lockfile, newdir, ni, packmail, Para, poly, rand, reconvert, regex, regsub, statcache, tb, tzparse, util, whatsound, whrandom, zmod

The following modules were removed in Python 2.6:

gopherlib, rgbimg, macfs

The following modules currently lack a DeprecationWarning:

rfc822, mimetools, multifile

Deprecated modules

Module name:   posixfile
Rationale:     Locking is better done by fcntl.lockf().
Date:          Before 1-Oct-2000.
Documentation: Already documented as obsolete.  Deprecation
               warning added in Python 2.6.

Module name:   gopherlib
Rationale:     The gopher protocol is not in active use anymore.
Date:          1-Oct-2000.
Documentation: Documented as deprecated since Python 2.5.  Removed
               in Python 2.6.

Module name:   rgbimgmodule
Rationale:     In a 2001-04-24 c.l.py post, Jason Petrone mentions
               that he occasionally uses it; no other references to
               its use can be found as of 2003-11-19.
Date:          1-Oct-2000
Documentation: Documented as deprecated since Python 2.5.  Removed
               in Python 2.6.

Module name:   pre
Rationale:     The underlying PCRE engine doesn't support Unicode, and
               has been unmaintained since Python 1.5.2.
Date:          10-Apr-2002
Documentation: It was only mentioned as an implementation detail,
               and never had a section of its own.   This mention
               has now been removed.

Module name:   whrandom
Rationale:     The module's default seed computation was
               inherently insecure; the random module should be
               used instead.
Date:          11-Apr-2002
Documentation: This module has been documented as obsolete since
               Python 2.1, but listing in this PEP was neglected.
               The deprecation warning will be added to the module
               one year after Python 2.3 is released, and the
               module will be removed one year after that.

Module name:   rfc822
Rationale:     Supplanted by Python 2.2's email package.
Date:          18-Mar-2002
Documentation: Documented as "deprecated since release 2.3" since
               Python 2.2.2.

Module name:   mimetools
Rationale:     Supplanted by Python 2.2's email package.
Date:          18-Mar-2002
Documentation: Documented as "deprecated since release 2.3" since
               Python 2.2.2.

Module name:   MimeWriter
Rationale:     Supplanted by Python 2.2's email package.
Date:          18-Mar-2002
Documentation: Documented as "deprecated since release 2.3" since
               Python 2.2.2.  Raises a DeprecationWarning as of
               Python 2.6.

Module name:   mimify
Rationale:     Supplanted by Python 2.2's email package.
Date:          18-Mar-2002
Documentation: Documented as "deprecated since release 2.3" since
               Python 2.2.2.  Raises a DeprecationWarning as of
               Python 2.6.

Module name:   rotor
Rationale:     Uses insecure algorithm.
Date:          24-Apr-2003
Documentation: The documentation has been removed from the library
               reference in Python 2.4.

Module name:   TERMIOS.py
Rationale:     The constants in this file are now in the 'termios' module.
Date:          10-Aug-2004
Documentation: This module has been documented as obsolete since
               Python 2.1, but listing in this PEP was neglected.
               Removed from the library reference in Python 2.4.

Module name:   statcache
Rationale:     Using the cache can be fragile and error-prone;
               applications should just use os.stat() directly.
Date:          10-Aug-2004
Documentation: This module has been documented as obsolete since
               Python 2.2, but listing in this PEP was neglected.
               Removed from the library reference in Python 2.5.

Module name:   mpz
Rationale:     Third-party packages provide similiar features
               and wrap more of GMP's API.
Date:          10-Aug-2004
Documentation: This module has been documented as obsolete since
               Python 2.2, but listing in this PEP was neglected.
               Removed from the library reference in Python 2.4.

Module name:   xreadlines
Rationale:     Using 'for line in file', introduced in 2.3, is preferable.
Date:          10-Aug-2004
Documentation: This module has been documented as obsolete since
               Python 2.3, but listing in this PEP was neglected.
               Removed from the library reference in Python 2.4.

Module name:   multifile
Rationale:     Supplanted by the email package.
Date:          21-Feb-2006
Documentation: Documented as deprecated as of Python 2.5.

Module name:   sets
Rationale:     The built-in set/frozenset types, introduced in
               Python 2.4, supplant the module.
Date:          12-Jan-2007
Documentation: Documented as deprecated as of Python 2.6.

Module name:   buildtools
Rationale:     Unknown.
Date:          15-May-2007
Documentation: Documented as deprecated as of Python 2.3, but
               listing in this PEP was neglected.  Raised a
               DeprecationWarning as of Python 2.6.

Module name:   cfmfile
Rationale:     Unknown.
Date:          15-May-2007
Documentation: Documented as deprecated as of Python 2.4, but
               listing in this PEP was neglected.  A
               DeprecationWarning was added in Python 2.6.

Module name:   macfs
Rationale:     Unknown.
Date:          15-May-2007
Documentation: Documented as deprecated as of Python 2.3, but
               listing in this PEP was neglected.  Removed in
               Python 2.6.

Module name:   md5
Rationale:     Replaced by the 'hashlib' module.
Date:          15-May-2007
Documentation: Documented as deprecated as of Python 2.5, but
               listing in this PEP was neglected.
               DeprecationWarning raised as of Python 2.6.

Module name:   sha
Rationale:     Replaced by the 'hashlib' module.
Date:          15-May-2007
Documentation: Documented as deprecated as of Python 2.5, but
               listing in this PEP was neglected.
               DeprecationWarning added in Python 2.6.

Module name:   plat-freebsd2/IN and plat-freebsd3/IN
Rationale:     Platforms are obsolete (last released in 2000)
               Removed from 2.6
Date:          15-May-2007
Documentation: None

Module name:   plat-freebsd4/IN and possibly plat-freebsd5/IN
Rationale:     Platforms are obsolete/unsupported
Date:          15-May-2007
               Remove from 2.7
Documentation: None

Module name:   formatter
Rationale:     Lack of use in the community, no tests to keep
               code working.
Documentation: Deprecated as of Python 3.4 by raising
               PendingDeprecationWarning. Slated for removal in
               Python 3.6.

Deprecation of modules removed in Python 3.0

PEP 3108 lists all modules that have been removed from Python 3.0. They all are documented as deprecated in Python 2.6, and raise a DeprecationWarning if the -3 flag is activated.