[issue13177] Avoid chained exceptions in lru_cache

[Raymond Hettinger]

Raymond Hettinger <raymond.hettinger at gmail.com> added the comment:

This changes behavior so that hash() gets called twice for the key tuple, resulting in decreased performance.

In an earlier version of the lru_cache before the "with lock" was introduced, the try/except form was more atomic.  It also worked well with dict subclasses that use __missing__ (which is bypassed with the LBYL style of lookup).

I'll look at this more shortly -- thanks for the links to the other tracker items.

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priority: normal -> low

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue13177>
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