168 lines
5.9 KiB
Plaintext
168 lines
5.9 KiB
Plaintext
PEP: 3003
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Title: Python Language Moratorium
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Version: $Revision$
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Last-Modified: $Date$
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Author: Brett Cannon, Jesse Noller, Guido van Rossum
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Status: Accepted
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Type: Process
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Content-Type: text/x-rst
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Created: 21-Oct-2009
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Post-History: 03-Nov-2009
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Abstract
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========
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This PEP proposes a temporary moratorium (suspension) of all changes
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to the Python language syntax, semantics, and built-ins for a period
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of at least two years from the release of Python 3.1. In particular, the
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moratorium would include Python 3.2 (to be released 18-24 months after
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3.1) but allow Python 3.3 (assuming it is not released prematurely) to
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once again include language changes.
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This suspension of features is designed to allow non-CPython implementations
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to "catch up" to the core implementation of the language, help ease adoption
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of Python 3.x, and provide a more stable base for the community.
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Rationale
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=========
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This idea was proposed by Guido van Rossum on the python-ideas [1]_ mailing
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list. The premise of his email was to slow the alteration of the Python core
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syntax, builtins and semantics to allow non-CPython implementations to catch
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up to the current state of Python, both 2.x and 3.x.
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Python, as a language is more than the core implementation --
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CPython -- with a rich, mature and vibrant community of implementations, such
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as Jython [2]_, IronPython [3]_ and PyPy [4]_ that are a benefit not only to
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the community, but to the language itself.
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Still others, such as Unladen Swallow [5]_ (a branch of CPython) seek not to
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create an alternative implementation, but rather they seek to enhance the
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performance and implementation of CPython itself.
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Python 3.x was a large part of the last several years of Python's
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development. Its release, as well as a bevy of changes to the language
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introduced by it and the previous 2.6.x releases, puts alternative
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implementations at a severe disadvantage in "keeping pace" with core python
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development.
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Additionally, many of the changes put into the recent releases of the language
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as implemented by CPython have not yet seen widespread usage by the
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general user population. For example, most users are limited to the version
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of the interpreter (typically CPython) which comes pre-installed with their
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operating system. Most OS vendors are just barely beginning to ship Python 2.6
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-- even fewer are shipping Python 3.x.
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As it is expected that Python 2.7 be the effective "end of life" of the Python
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2.x code line, with Python 3.x being the future, it is in the best interest of
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Python core development to temporarily suspend the alteration of the language
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itself to allow all of these external entities to catch up and to assist in
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the adoption of, and migration to, Python 3.x
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Finally, the moratorium is intended to free up cycles within core development
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to focus on other issues, such as the CPython interpreter and improvements
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therein, the standard library, etc.
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This moratorium does not allow for exceptions -- once accepted, any pending
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changes to the syntax or semantics of the language will be postponed until the
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moratorium is lifted.
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This moratorium does not attempt to apply to any other Python implementation
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meaning that if desired other implementations may add features which deviate
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from the standard implementation.
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Details
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=======
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Cannot Change
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-------------
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* New built-ins
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* Language syntax
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The grammar file essentially becomes immutable apart from ambiguity
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fixes.
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* General language semantics
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The language operates as-is with only specific exemptions (see
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below).
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* New __future__ imports
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These are explicitly forbidden, as they effectively change the language
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syntax and/or semantics (albeit using a compiler directive).
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Case-by-Case Exemptions
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-----------------------
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* New methods on built-ins
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The case for adding a method to a built-in object can be made.
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* Incorrect language semantics
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If the language semantics turn out to be ambiguous or improperly
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implemented based on the intention of the original design then the
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semantics may change.
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* Language semantics that are difficult to implement
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Because other VMs have not begun implementing Python 3.x semantics
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there is a possibility that certain semantics are too difficult to
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replicate. In those cases they can be changed to ease adoption of
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Python 3.x by the other VMs.
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Allowed to Change
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-----------------
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* C API
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It is entirely acceptable to change the underlying C code of
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CPython as long as other restrictions of this moratorium are not
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broken. E.g. removing the GIL would be fine assuming certain
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operations that are currently atomic remain atomic.
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* The standard library
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As the standard library is not directly tied to the language
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definition it is not covered by this moratorium.
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* Backports of 3.x features to 2.x
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The moratorium only affects features that would be new in 3.x.
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* Import semantics
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For example, PEP 382. After all, import semantics vary between
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Python implementations anyway.
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Retroactive
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===========
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It is important to note that the moratorium covers all changes since the release
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of Python 3.1. This rule is intended to avoid features being rushed or smuggled
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into the CPython source tree while the moratorium is being discussed. A review
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of the NEWS file for the py3k development branch showed no commits would need to
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be rolled back in order to meet this goal.
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Extensions
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==========
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The time period of the moratorium can only be extended through a new PEP.
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Copyright
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=========
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This document has been placed in the public domain.
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References
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==========
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.. [1] http://mail.python.org/pipermail/python-ideas/2009-October/006305.html
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.. [2] http://www.jython.org/
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.. [3] http://www.codeplex.com/IronPython
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.. [4] http://codespeak.net/pypy/
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.. [5] http://code.google.com/p/unladen-swallow/
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..
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Local Variables:
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mode: indented-text
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indent-tabs-mode: nil
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sentence-end-double-space: t
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fill-column: 80
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coding: utf-8
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End:
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