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~
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