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

[Alex Gaynor]

Alex Gaynor added the comment:

That strategy only works if you know the exact count, it fails if you only have an estimate (as __length_hint__ gives you).

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue17338>
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