Static caching property
Ethan Furman
ethan at stoneleaf.us
Mon Mar 21 13:45:35 EDT 2016
On 03/21/2016 10:03 AM, Joseph L. Casale wrote:
>> One solution is to use descriptor protocol on the class, which means
>> using a metaclass. I'm not sure it's the best option, but it is an
>> option.
>
> I will look at that, I wonder if however I am not over complicating it:
>
> class Foo:
> _bar = None
> @property
> def expensive(self):
> if Foo._bar is None:
> import something
> Foo._bar = something.expensive()
> return Foo._bar
>
> Somewhat naive, but a test with if is pretty cheap...
A slightly cleaner approach (but only slightly):
class Cache(object):
_sentinal = object()
def __init__(self, expensive_func):
self.value = self._sentinal
self.func = expensive_func
def __get__(self, *args):
if self.value is self._sentinal:
self.value = self.func()
return self.func()
The advantages:
- only one location in the class
- works correctly whether accessed via class or instance
- clue as to functionality in the name
--
~Ethan~
More information about the Python-list
mailing list