[Python-ideas] Proposal: Moratorium on Python language changes (original) (raw)

Guido van Rossum guido at python.org
Wed Oct 21 18:42:01 CEST 2009

I propose a moratorium on language changes. This would be a period of several years during which no changes to Python's grammar or language semantics will be accepted. The reason is that frequent changes to the language cause pain for implementors of alternate implementations (Jython, IronPython, PyPy, and others probably already in the wings) at little or no benefit to the average user (who won't see the changes for years to come and might not be in a position to upgrade to the latest version for years after).

The main goal of the Python development community at this point should be to get widespread acceptance of Python 3000. There is tons of work to be done before we can be comfortable about Python 3.x, mostly in creating solid ports of those 3rd party libraries that must be ported to Py3k before other libraries and applications can be ported. (Other work related to Py3k acceptance might be tools to help porting, tools to help maintaining multiple versions of a codebase, documentation about porting to Python 3, and so on. Also, work like that going on in the distutils-sig is very relevant.)

Note, the moratorium would only cover the language itself plus built-in functions, not the standard library. Development in the standard library is valuable and much less likely to be a stumbling block for alternate language implementations. I also want to exclude details of the CPython implementation, including the C API from being completely frozen -- for example, if someone came up with (otherwise acceptable) changes to get rid of the GIL I wouldn't object.

But the moratorium would clearly apply to proposals for anonymous blocks, "yield from" (PEP 380), changes to decorator syntax, and the like. (I'm sure it won't stop discussion of those proposals, and that's not the purpose of the moratorium; but at least it will stop worries elsewhere that such proposals might actually be accepted any time soon.)

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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