python-peps/pep-3108.txt

PEP: 3108
Title: Standard Library Reorganization
Version: $Revision$
Last-Modified: $Date$
Author: Brett Cannon <brett@python.org>
Status: Draft
Type: Standards Track
Content-Type: text/x-rst
Created: 01-Jan-2007
Python-Version: 3.0
Post-History: 


Abstract
========

Just like the language itself, Python's standard library (stdlib) has
grown over the years to be very rich.  But over time some modules
have lost their need to be included with Python.  There has also been
an introduction of a naming convention for modules since Python's
inception that not all modules follow.

Python 3.0 has presented a chance to remove modules that do not have
long term usefulness.  This chance also allows for the renaming of
modules so that they follow the Python style guide [#pep-0008]_.  This
PEP lists modules that should not be included in Python 3.0 and what
modules need to be renamed.


Modules to Remove
=================

Guido pronounced that "silly old stuff" is to be deleted from the
stdlib for Py3K [#silly-old-stuff]_.  This is open-ended on purpose.
Each module to be removed needs to have a justification as to why it
should no longer be distributed with Python.  This can range from the
module being deprecated in Python 2.x to being for a platform that is
no longer widely used.

This section of the PEP lists the various modules to be removed. Each
subsection represents a different reason for modules to be
removed.  Each module must have a specific justification on top of
being listed in a specific subsection so as to make sure only modules
that truly deserve to be removed are in fact removed.

When a reason mentions how long it has been since a module has been
"uniquely edited", it is in reference to how long it has been since a
checkin was done specifically for the module and not for a change that
applied universally across the entire stdlib.  If an edit time is not
denoted as "unique" then it is the last time the file was edited,
period.

The procedure to thoroughly remove a module is:

#. Remove the module.
#. Remove the tests.
#. Edit ``Modules/Setup.dist`` and ``setup.py`` if needed.
#. Change all references to the removed module in the standard
   library.
#. Remove the docs.
#. Delete the reference to the removed docs in ``Doc/Makefile.deps``
   and ``Doc/lib/lib.tex``.
#. If possible, build the docs. (cd Doc ; make)
#. Run the regression test suite; watch out for tests that are skipped
   because an import failed for the removed module.

If a deprecation warning is added to 2.6, it would be better to make
all the changes to 2.6, merge the changes into the 3k branch, then
perform the procedure above.  This will avoid some merge conflicts.


Previously deprecated
---------------------

PEP 4 lists all modules that have been deprecated in the stdlib
[#pep-0004]_.  All modules listed in the PEP at the time of the first
alpha release of Python 3.0 will be removed.

The entire contents of lib-old will also be removed.  These modules
have already been removed from being imported but are kept in the
distribution for Python for users that rely upon the code.


Platform-specific with minimal use
----------------------------------

Python supports many platforms, some of which are not widely held.
And on some of these platforms there are modules that have limited use
to people on those platforms.  Because of their limited usefulness it
would be better to no longer burden the Python development team with
their maintenance.

* IRIX (which is no longer produced [#irix-retirement]_)

  + AL/al [done]

    - Provides sound support on Indy and Indigo workstations.
    - Both workstations are no longer available.
    - Code has not been uniquely edited in three years.

  + cd [done]

    - CD drive control for SGI systems.
    - SGI no longer sells machines with IRIX on them.
    - Code has not been uniquely edited in 14 years.

  + cl [done]

    - Compression library for SGI systems.
    - SGI no longer sells machines with IRIX on them.
    - Code has not been uniquely edited in 14 years.

  + DEVICE/GL/gl/cgen/cgensuport [done]

    - OpenGL access.
    - Has not been edited in at least eight years.
    - Third-party libraries provide better support (PyOpenGL [#pyopengl]_).

  + FL/fl/flp [done]

    - Wrapper for the FORMS library [#irix-forms]_
    - FORMS has not been edited in 12 years.
    - Library is not widely used.
    - First eight hits on Google are for Python docs for fl.

  + fm [done]

    - Wrapper to the IRIS Font Manager library.
    - Only available on SGI machines which no longer come with IRIX.

  + imgfile [done]

    - Wrapper for SGI libimage library for imglib image files
      (``.rgb`` files).
    - Python Imaging Library provdes read-only support [#pil]_.
    - Not uniquely edited in 13 years.

  + jpeg [done]

    - Wrapper for JPEG (de)compressor.
    - Code not uniquely edited in nine years.
    - Third-party libraries provide better support
      (Python Imaging Library [#pil]_).

* Solaris

  + SUNAUDIODEV/sunaudiodev [done]

    - Access to the sound card on Sun machines.
    - Code not uniquely edited in over eight years.

* Mac

  + aetools/aepack/aetypes/MiniAEFrame

    - OSA support is better through third-party modules.
        
        * Appscript [#appscript]_.

    - Hard-coded endianness which breaks on Intel Macs.
    - Might need to rename if Carbon package dependent.

  + applesingle

    - Undocumented.
    - AppleSingle is a binary file format for A/UX.
    - A/UX no longer distributed.

  + autoGIL

    - Very bad model for using Python with the CFRunLoop.
    - Rename to _autogil if needed by Carbon package.

  + Carbon.CF
  
    - Half-heared attempt.

  + findertools

    - No longer useful.

  + FrameWork

    - Poorly documented.
    - Not updated to support Carbon Events.

  + icopen

     - Not needed on OS X.
     - Meant to replace 'open' which is usually a bad thing to do.

  + videoreader

     - No longer used.

  + W

     - No longer distributed with Python.


Hardly used
------------

Some modules that are platform-independent are hardly used.  This
can be from how easy it is to implement the functionality from scratch
or because the audience for the code is very small.

* audiodev [done]

  + Undocumented.
  + Not edited in five years.
  + If removed sunaudio should go as well (also undocumented; not
    edited in over seven years).

* imputil

  + Undocumented.
  + Never updated to support absolute imports.

* mutex

  + Easy to implement using a semaphore and a queue.
  + Cannot block on a lock attempt.
  + Not uniquely edited since its addition 15 years ago.

* repr

  + Controls output of the repr of objects.
  + String slicing and string interpolation can do similar work.
  + Used by pdb, but do not need to expose API.

* stringold [done]

  + Function versions of the methods on string objects.
  + Obsolete since Python 1.6.
  + Any functionality not in the string object or module will be moved
    to the string module (mostly constants).

* symtable/_symtable

  + Undocumented.

* toaiff [done, moved to Demo]

  + Undocumented.
  + Requires ``sox`` library to be installed on the system.

* user

  + Easily handled by allowing the application specify its own
    module name, check for existence, and import if found.

* new [done]

  + Just a rebinding of names from the 'types' module.
  + Can also call ``type`` built-in to get most types easily.
  + Docstring states the module is no longer useful as of revision
    27241 (2002-06-15).

* pure [done]

  + Written before Pure Atria was bought by Rational which was then
    bought by IBM (in other words, very old).


Obsolete
--------

Becoming obsolete signifies that either another module in the stdlib
or a widely distributed third-party library provides a better solution
for what the module is meant for.

* Bastion/rexec [done]

  + Restricted execution / security.
  + Turned off in Python 2.3.
  + Modules deemed unsafe.

* bsddb185 [done]

  + Superceded by bsddb3
  + Not built by default.
  + Documentation specifies that the "module should never be used
    directly in new code".

* commands [only getstatus(), does whole module go?]/popen2 [done]

  + subprocess module replaces them [#pep-0324]_.

* compiler (need to add AST -> bytecode mechanism) [done - removal]

  + Having to maintain both the built-in compiler and the stdlib
    package is redundant [#ast-removal]_.
  + The AST created by the compiler is available [#ast]_.
  + Mechanism to compile from an AST needs to be added.

* dl

  + ctypes provides better support for same functionality.

* fpformat

  + All functionality is supported by string interpolation.

* ihooks

  + Undocumented.
  + For use with rexec which has been turned off since Python 2.3.

* imageop [done]

  + Better support by third-party libraries
    (Python Imaging Library [#pil]_).
  + Unit tests relied on rgbimg and imgfile.
        - rgbimg was removed in Python 2.6.
        - imgfile slated for removal in this PEP. [done]

* linuxaudiodev [done]

  + Replaced by ossaudiodev.

* sched

  + Replaced by threading.Timer.

* stat

  + ``os.stat`` now returns a tuple with attributes.
  + Functions in the module should be made into methods for the object
    returned by os.stat.

* statvfs

  + ``os.statvfs`` now returns a tuple with attributes.

* thread

  + People should use 'threading' instead.

    - Rename 'thread' to _thread.
    - Deprecate dummy_thread and rename _dummy_thread.
    - Move thread.get_ident over to threading.

  + Guido has previously supported the deprecation
    [#thread-deprecation]_.


Modules to Rename
=================

Along with the stdlib gaining some modules that are no longer
relevant, there is also the issue of naming.  Many modules existed in
the stdlib before PEP 8 came into existence [#pep-0008]_.  This has
led to some naming inconsistencies and namespace bloat that should be
addressed.

Any module that has been suggested for removal and does not meet the
required naming scheme is *not* listed below.


PEP 8 violations
----------------

PEP 8 specifies that modules "should have short, all-lowercase names"
where "underscores can be used ... if it improves readability"
[#pep-0008]_.  The use of underscores is discouraged in package names.

==================  ==================================================
Current Name        Replacement Name
==================  ==================================================
_winreg             winreg (rename also because module has a public
                    interface and thus should not have a leading
                    underscore)
Carbon              carbon
ColorPicker         colorpicker
ConfigParser        configparser
Cookie              cookie
copy_reg            copyreg
EasyDialogs         easydialogs
HTMLParser          htmlparser
MacOS               macos
Nav                 nav
PixMapWrapper       pixmap_wrapper
Queue               queue
ScrolledText        scrolledtext
SocketServer        socketserver
Tix                 tix
Tkinter             tkinter
UserDict            userdict
UserList            userlist
UserString          userstring
==================  ==================================================


Merging C and Python implementations of the same interface
----------------------------------------------------------

Several interfaces have both a Python and C implementation.  While it
is great to have a C implementation for speed with a Python
implementation as fallback, there is no need to expose the two
implementations independently in the stdlib.  For Python 3.0 all
interfaces with two implementations will be merged into a single
public interface.

The C module is to be given a leading underscore to delineate the fact
that it is not the reference implementation (the Python implementation
is).  This means that any semantic difference between the C and Python
versions must be dealt with before Python 3.0 or else the C
implementation will be removed until it can be fixed.

One interface that is not listed below is xml.etree.ElementTree.  This
is an externally maintained module and thus is not under the direct
control of the Python development team for renaming.  See `Open
Issues`_ for a discussion on this.

* pickle/cPickle

  + Rename cPickle to _pickle.
  + Semantic completeness of C implementation *not* verified.

* profile/cProfile

  + Rename cProfile to _profile.
  + Semantic completeness of C implementation *not* verified.

* StringIO/cStringIO [done]

  + Added to the 'io' module as stringio.


No public, documented interface
-------------------------------

There are several modules in the stdlib that have no defined public
interface.  These modules exist as support code for other modules that
are exposed.  Because they are not meant to be used directly they
should be renamed to reflect this fact.

============  ===============================
Current Name  Replacement Name
============  ===============================
bdb           _bdb
markupbase    _markupbase [done]
opcode        _opcode
dummy_thread  _dummy_thread [#]_
============  ===============================

.. [#] Assumes ``thread`` is renamed to ``_thread``.


Poorly chosen names
-------------------

A few modules have names that were poorly chosen in hindsight.  They
should be renamed so as to prevent their bad name from perpetuating
beyond the 2.x series.

=================  ===============================
Current Name       Replacement Name
=================  ===============================
test.test_support  test.support
=================  ===============================


Grouping of modules
-------------------

As the stdlib has grown, several areas within it have expanded to
include multiple modules (e.g., dbm support). Thus some new packages
make sense where the renaming makes a module's name easier to work
with.


dbm package
///////////

=================  ===============================
Current Name       Replacement Name
=================  ===============================
anydbm             dbm.tools [1]_
dbhash             dbm.db
dbm                dbm.ndbm
dumbdm             dbm.dumb
gdbm               dbm.gnu
whichdb            dbm.tools [1]_
=================  ===============================


.. [1] ``dbm.tools`` can combine ``anybdbm`` and ``whichdb`` since the public
       API for both modules has no name conflict.


http package
////////////

=================  ===============================
Current Name       Replacement Name
=================  ===============================
httplib            http.client
BaseHTTPServer     http.server [2]_
CGIHTTPServer      http.server [2]_
SimpleHTTPServer   http.server [2]_
=================  ===============================

.. [2] The ``http.server`` module can combine the specified modules
       safely as they have no naming conflicts.
       
       
xmlrpc package
//////////////

==================  ===============================
Current Name        Replacement Name
==================  ===============================
xmlrpclib           xmlrpc.client
SimpleXMLRPCServer  xmlrpc.server [3]_
CGIXMLRPCServer     xmlrpc.server [3]_
==================  ===============================

.. [3] The modules being combined into ``xmlrpc.server`` have no
       naming conflicts and thus can safely be merged.


Transition Plan
===============

For modules to be removed
-------------------------

For the removal of modules that are continuing to exist in the Python
2.x series (i.e., not deprecated explicitly in the 2.x series), a
proper warning will be set that is silenced by default;
PendingDeprecationWarning initially, moving over to a Py3K-specific
warning later if one comes into existence.


Renaming of modules
-------------------

For modules that are renamed, stub modules will be created with the
original names and be kept in a package within the stdlib.  The need
to keep them within a package is to prevent naming conflicts
with case-insensitive filesystems. 

These stub modules will import the module code based on the new
naming.  The same type of warning being raised by modules being
removed will be raised in the stub modules.

Support in the 2to3 refactoring tool for renames will also be used
[#2to3]_.  Import statements will be rewritten so that only the import
statement and none of the rest of the code needs to be touched.  This
will be accomplished by using the ``as`` keyword in import statements
to bind in the module namespace to the old name while importing based
on the new name.


Open Issues
===========

Renaming of modules maintained outside of the stdlib
----------------------------------------------------

xml.etree.ElementTree not only does not meet PEP 8 naming standards
but it also has an exposed C implementation [#pep-0008]_.  It is an
externally maintained package, though [#pep-0360]_.  A request will be
made for the maintainer to change the name so that it matches PEP 8
and hides the C implementation.


Rejected Ideas
==============

Modules that were originally suggested for removal 
--------------------------------------------------

* asynchat/asyncore

  + Josiah Carlson has said he will maintain the modules.

* base64/quopri/uu

  + All still widely used.
  + 'codecs' module does not provide as nice of an API for basic
    usage.

* fileinput

  + Useful when having to work with stdin.

* nis

  + Testimonials from people that new installations of NIS are still
    occurring

* getopt

  + Simpler than optparse.

* telnetlib

  + Really handy for quick-and-dirty remote access.
  + Some hardware supports using telnet for configuration and
    querying.


Introducing a new top-level package
-----------------------------------

It has been suggested that the entire stdlib be placed within its own
package.  This PEP will not address this issue as it has its own
design issues (naming, does it deserve special consideration in import
semantics, etc.).  Everything within this PEP can easily be handled if
a new top-level package is introduced.


Introducing new packages to contain theme-related modules
---------------------------------------------------------

During the writing of this PEP it was noticed that certain themes
appeared in the stdlib.  In the past people have suggested introducing
new packages to help collect modules that share a similar theme (e.g.,
audio).  An Open Issue was created to suggest some new packages to
introduce.

In the end, though, not enough support could be pulled together to
warrant moving forward with the idea.  Instead name simplification has
been chosen as the guiding force for PEPs to create.


References
==========

.. [#pep-0004] PEP 4: Deprecation of Standard Modules
    (http://www.python.org/dev/peps/pep-0004/)

.. [#pep-0008] PEP 8: Style Guide for Python Code
    (http://www.python.org/dev/peps/pep-0008/)

.. [#pep-0324] PEP 324: subprocess -- New process module
    (http://www.python.org/dev/peps/pep-0324/)

.. [#pep-0360] PEP 360: Externally Maintained Packages
    (http://www.python.org/dev/peps/pep-0360/)

.. [#module-index] Python Documentation: Global Module Index
    (http://docs.python.org/modindex.html)

.. [#timing-module] Python Library Reference: Obsolete
    (http://docs.python.org/lib/obsolete-modules.html)

.. [#silly-old-stuff] Python-Dev email: "Py3k release schedule worries"
    (http://mail.python.org/pipermail/python-3000/2006-December/005130.html)

.. [#thread-deprecation] Python-Dev email: Autoloading?
    (http://mail.python.org/pipermail/python-dev/2005-October/057244.html)

.. [#py-dev-summary-2004-11-01] Python-Dev Summary: 2004-11-01
    (http://www.python.org/dev/summary/2004-11-01_2004-11-15/#id10)

.. [#2to3] 2to3 refactoring tool
    (http://svn.python.org/view/sandbox/trunk/2to3/)

.. [#pyopengl] PyOpenGL
    (http://pyopengl.sourceforge.net/)

.. [#pil] Python Imaging Library (PIL)
    (http://www.pythonware.com/products/pil/)

.. [#twisted] Twisted
    (http://twistedmatrix.com/trac/)

.. [#irix-retirement] SGI Press Release:
    End of General Availability for MIPS IRIX Products -- December 2006
    (http://www.sgi.com/support/mips_irix.html)

.. [#irix-forms] FORMS Library by Mark Overmars
    (ftp://ftp.cs.ruu.nl/pub/SGI/FORMS)

.. [#sun-au] Wikipedia: Au file format
    (http://en.wikipedia.org/wiki/Au_file_format)

.. [#appscript] appscript
    (http://appscript.sourceforge.net/)

.. [#ast] _ast module
    (http://docs.python.org/lib/ast.html)

.. [#ast-removal] python-dev email: getting compiler package failures
    (http://mail.python.org/pipermail/python-3000/2007-May/007615.html)


Copyright
=========

This document has been placed in the public domain.



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