..

Copyright 2009-2017 Ram Rachum. This work is licensed under a Creative

Commons Attribution-ShareAlike 3.0 Unported License, with attribution to

"Ram Rachum at ram.rachum.com" including link. The license may be obtained

at http://creativecommons.org/licenses/by-sa/3.0/

.. _topics-caching-cached-type:

:class:`caching.CachedType`

===========================

A class that automatically caches its instances

-----------------------------------------------

Sometimes you define classes whose instances hold absolutely no state on them,

and are completey determined by the arguments passed to them. In these cases

using :class:`caching.CachedType` as a metaclass would cache class instances,

preventing more than one of them from being created:

>>> from python_toolbox import caching

>>>

>>> class A(metaclass=caching.CachedType):

... def __init__(self, a=1, b=2):

... self.a = a

... self.b = b

Now every time you create an instance, it'll be cached:

>>> my_instance = A(b=3)

And the next time you'll create an instance with the same arguments:

>>> another_instance = A(b=3)

No instance will be actually created; the same instance from before will be used:

>>> assert another_instance is my_instance