[Python-3000] pre-PEP: Process for reviewing/improving stdlib modules in 3.0

[Georg Brandl]

PEP: XXX
Title: Procedure for changing standard library modules
Version: $Revision$
Last-Modified: $Date$
Author: Georg Brandl <g.brandl at gmx.net>
Status: Draft
Type: Informational
Content-Type: text/x-rst
Created: 02-Apr-2006


Abstract
========

This PEP describes the procedure for reviewing and improving standard
library modules, especially those written in Python, making them ready
for Python 3000.  There can be different steps of refurbishing, each
of which is described in a section below.


Step 1: Removal of obsolete modules
===================================

All modules marked as deprecated in 2.x versions should be removed for
Python 3000.  The same applies to modules which are seen as obsolete today,
but are too widely used to be deprecated or removed.  Python 3000 is the
big occasion to get rid of them.

There will have to be a document listing all removed modules, together
with information on possible substitutes or alternatives.  This infor-
mation will also have to be provided by the python3warn.py porting
helper script mentioned in PEP XXX.


Step 2: Renaming modules
========================

Aside from a "great stdlib renaming" introducing a hierarchic library
namespace or a top-level package from which to import standard modules,
some modules' names are known to have been chosen unwisely, a mistake
which could never be corrected in the 2.x series.  Examples are names
like "StringIO" or "Cookie".  For Python 3000, there will be the possi-
bility to rename those modules to less confusing and more conforming
names.

Of course, each rename will have to be stated in the documentation of
the respective module and perhaps in the global document of Step 1.
Additionally, the python3warn.py script will recognize the old module
names and notify the user accordingly.


Step 3: Code cleanup
====================

As most library modules written in Python have not been touched except
for bug fixes, following the policy of never changing a running system,
many of them may contain code that is not up to the newest language
features and could be rewritten in a more concise, modern Python.

As long as these changes don't change the module's interface and behavior,
no documentation updates are necessary.


Step 4: Enhancement of test coverage
====================================

Code coverage by unit tests varies greatly between modules.  Each test
suite should be checked for completeness, and the remaining classic tests
should be converted to PyUnit (or whatever new shiny testing framework
comes with Python 3000, perhaps py.test?).

No documentation changes are necessary for this step.


Step 5: Unification of module metadata
======================================

This is a small and probably not very important step.  There have been
various attempts at providing author, version and similar metadata in
modules (such as a "__version__" global).  Those could be standardized
and used throughout the library.

No documentation changes are necessary for this step, too.


Step 6: Backwards incompatible bug fixes
========================================

Over the years, many bug reports have been filed which complained about
bugs in standard library modules, but have subsequently been closed as
"Won't fix" since a fix would have introduced a major incompatibility
which was not acceptable in the Python 2.x series.  In Python 3000, the
fix can be applied if the interface per se is still acceptable.

Each slight behavioral change caused by such fixes must be mentioned in
the documentation, perhaps in a "Changed in Version 3.0" paragraph.


Step 7: Interface changes
=========================

The last and most disruptive change is the overhaul of a module's public
interface.  If a module's interface is to be changed, a justification
should be made beforehand, or a PEP should be written.

The change must be fully documented as "New in Version 3.0", and the
python3warn.py script must know about it.


References
==========

TBD

Copyright
=========

This document has been placed in the public domain.