[issue21145] Add the @cached_property decorator

[Omer Katz]

Omer Katz added the comment:

The default implementation should simple:
Once the property is accessed for the first time calculate the result and
never calculate again.
It's what both Django & pip uses.
You can add an optional TTL.
There aren't any other features I can come up with that are common enough.
If needed, one can inherit from cached_property and do whatever is needed.
Eric, Why don't you think a C implementation is needed? It's a simple
operation for sure but it is meant to increase runtime efficiency.

2014-04-05 1:11 GMT+04:00 Éric Araujo <report at bugs.python.org>:

>
> Éric Araujo added the comment:
>
> It could make sense to add clean, working recipes to e.g. the functools
> documentation.  The cached_property in the wiki uses a TTL, other like
> Pyramid's reify decorator make properties that ensure the fget function is
> called only once per instance, and there may be subtly different variants
> out there.  I don't know if there's a universally useful variant that
> should be added to the sdlib right now.  (I don't think a C implementation
> is needed.)
>
> On a related note, the Python docs about desciptors may be missing
> entry-level explanations, as described here:
> http://me.veekun.com/blog/2012/05/23/python-faq-descriptors/
>
> ----------
> nosy: +eric.araujo, rhettinger
>
> _______________________________________
> Python tracker <report at bugs.python.org>
> <http://bugs.python.org/issue21145>
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