When we were discussing yield from, Guido mentioned that it would be nice to have some way to test out things like that before committing all of Python to it. One way to do that might be if someone adapted it into a "4-to-3" to let you rewrite yield from, for example, in its full Python 3.2 expansion form. In other words, the n-to-n engine could be used as a general purpose macro system. Perhaps it could even useful for the internationalization project mentioned recently? 

The advantage of having the macro engine separate from Python proper would be that this way these extensions never get popular, and so 99% of Pythonistas never have to worry that maybe someone redefined "for item in items:" in their module using C-style #macros. It would exist solely as a way of testing out the various proposals that are made on Python-ideas and elsewhere before having to commit to them or of translating Python programs into a native language for younger, non-English native programmers.

-- Carl 

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