[issue17338] Add length_hint parameter to list, dict, set constructors to allow efficient presizing

[Charles-François Natali]

Charles-François Natali added the comment:

> Here is an experimental patch. The speedup is ... measurable.

It's likely to be more useful for dict and set, to avoid/limit rehashs.
Also, the allocation overhead depends on the implementation, I suspect the gain would be more important with PyPy.

FWIW, Java proposes this for lists and maps, but I'm not convinced exposing such tunables really makes sense for Python.

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nosy: +neologix

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<http://bugs.python.org/issue17338>
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