[Python-checkins] r76092 - peps/trunk/pep-3003.txt

Tue Nov 3 18:26:45 CET 2009

Author: guido.van.rossum
Date: Tue Nov 3 18:26:45 2009
New Revision: 76092
Log:
Initial checkin of Moratorium PEP.
Added:
 peps/trunk/pep-3003.txt
Added: peps/trunk/pep-3003.txt
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+PEP: 3003
+Title: Python Language Moratorium
+Version: $Revision$
+Last-Modified: $Date$
+Author: Brett Cannon, Jesse Noller, Guido van Rossum
+Status: Draft
+Type: Process
+Content-Type: text/x-rst
+Created: 21-Oct-2009
+Post-History:
+
+
+Abstract
+========
+
+This PEP proposes a temporary moratorium (suspension) of all changes
+to the Python language syntax, semantics, and built-ins for a period
+of at least two years from the release of Python 3.1.
+
+This suspension of features is designed to allow non-CPython implementations
+to "catch up" to the core implementation of the language, help ease adoption
+of Python 3.x, and provide a more stable base for the community.
+
+
+Rationale
+=========
+
+This idea was proposed by Guido van Rossum on the python-ideas [1]_ mailing
+list. The premise of his email was to slow the alteration of the Python core
+syntax, builtins and semantics to allow non-CPython implementations to catch
+up to the current state of Python, both 2.x and 3.x.
+
+Python, as a language is more than the core implementation --
+CPython -- with a rich, mature and vibrant community of implementations, such
+as Jython [2]_, IronPython [3]_ and PyPy [4]_ that are a benefit not only to
+the community, but to the language itself.
+
+Still others, such as Unladen Swallow [5]_ (a branch of CPython) seek not to
+create an alternative implementation, but rather they seek to enhance the
+performance and implementation of CPython itself.
+
+Python 3.x was a large part of the last several years of Python's
+development. Its release, as well as a bevy of changes to the language
+introduce by it and the previous 2.6.x releases, puts alternative
+implementations at a severe disadvantage in "keeping pace" with core python
+development.
+
+Additionally, many of the changes put into the recent releases of the language
+as implemented by CPython have not yet seen widespread usage amongst the
+general user population. For example, most users are beholden to the version
+of the interpreter (typically CPython) which comes pre-installed with their
+operating system. Most OS vendors are just barely beginning to ship Python 2.6
+-- even fewer are shipping Python 3.x.
+
+As it is expected that Python 2.7 be the effective "end of life" of the Python
+2.x code line, with Python 3.x being the future, it is in the best interest of
+Python core development to temporarily suspend the alteration of the language
+itself to allow all of these external entities to catch up and to assist in
+the adoption of, and migration to, Python 3.x
+
+Finally, the moratorium is intended to free up cycles within core development
+to focus on other issues, such as the CPython interpreter and improvements
+therein, the standard library, etc.
+
+This moratorium does not allow for exceptions -- once accepted, any pending
+changes to the syntax or semantics of the language will be postponed until the
+moratorium is lifted.
+
+This moratorium does not attempt to apply to any other Python implementation
+meaning that if desired other implementations may add features which deviate
+from the standard implementation.
+
+
+Details
+=======
+
+Cannot Change
+-------------
+
+* New built-ins
+* Language syntax
+ The grammar file essentially becomes immutable apart from ambiguity
+ fixes.
+* General language semantics
+ The language operates as-is with only specific exemptions (see
+ below).
+
+
+Case-by-Case Exemptions
+-----------------------
+
+* New methods on built-ins
+ The case for adding a method to a built-in object can be made.
+* Incorrect language semantics 
+ If the language semantics turn out to be ambiguous or improperly
+ implemented based on the intention of the original design then the
+ semantics may change.
+* Language semantics that are difficult to implement
+ Because other VMs have not begun implementing Python 3.x semantics
+ there is a possibility that certain semantics are too difficult to
+ replicate. In those cases they can be changed to ease adoption of
+ Python 3.x by the other VMs.
+
+
+Allowed to Change
+-----------------
+
+* C API
+ It is entirely acceptable to change the underlying C code of
+ CPython as long as other restrictions of this moratorium are not
+ broken. E.g. removing the GIL would be fine assuming certain
+ operations that are currently atomic remain atomic.
+* The standard library
+ As the standard library is not directly tied to the language
+ definition it is not covered by this moratorium.
+* Backports of 3.x features to to 2.x
+ The moratorium only affects features that would be new in 3.x.
+
+
+Retroactive
+===========
+
+It is important to note that the moratorium covers all changes since the
+release of Python 3.1. This rule is intended to avoid features being rushed or
+smuggled into the CPython source tree while the moratorium is being discussed.
+
+
+Copyright
+=========
+
+This document has been placed in the public domain.
+
+References
+==========
+
+.. [1] http://mail.python.org/pipermail/python-ideas/2009-October/006305.html
+.. [2] http://www.jython.org/
+.. [3] http://www.codeplex.com/IronPython
+.. [4] http://codespeak.net/pypy/
+.. [5] http://code.google.com/p/unladen-swallow/ 
+
+
+..
+ Local Variables:
+ mode: indented-text
+ indent-tabs-mode: nil
+ sentence-end-double-space: t
+ fill-column: 80
+ coding: utf-8
+ End:
