[issue21145] Add the @cached_property decorator

[Omer Katz]

New submission from Omer Katz:

cached properties are widely used in various prominent Python projects such as Django and pip (and many more).
They are not very complicated and there are proven implementation out there. Unfortunately there are way too many of them. This situation leads me to suggest adding it to the builtins.

Possible benefits:
* Implementation in C can improve caching performance
* Standardized implementation that can be used anywhere

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messages: 215439
nosy: Omer.Katz
priority: normal
severity: normal
status: open
title: Add the @cached_property decorator
type: enhancement
versions: Python 3.5

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue21145>
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