[issue29724] Itertools docs propose a harmful “speedup” without any explanation

[Marc-Andre Lemburg]

Marc-Andre Lemburg added the comment:

The localization using keyword parameters is a very old trick to avoid global lookups. It does give a noticeable speedup, esp. when the localized variables are used in tight loops or the function itself is used in such loops.

The 5% speedup Steven measured matches my experience with this trick as well. In some cases, it can provide a more dramatic speedup, but this depends a lot on how the code is written.

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nosy: +lemburg

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