import collections
import functools
class memoized(object):
'''Decorator. Caches a function's return value each time it is called.
If called later with the same arguments, the cached value is returned
(not reevaluated).
'''
def __init__(self, func):
self.func = func
self.cache = {}
def __call__(self, *args):
if not isinstance(args, collections.Hashable):
# uncacheable. a list, for instance.
# better to not cache than blow up.
return self.func(*args)
if args in self.cache:
return self.cache[args]
else:
value = self.func(*args)
self.cache[args] = value
return value
def __repr__(self):
'''Return the function's docstring.'''
return self.func.__doc__
def __get__(self, obj, objtype):
'''Support instance methods.'''
return functools.partial(self.__call__, obj)
# simple class just to test
class Fib(object):
@memoized
def fibonacci(self, n):
'''Return the nth fibonacci number.'''
if n in (0, 1):
return n
return self.fibonacci(n-1) + self.fibonacci(n-2)
im having trouble understanding how the get descriptor works here i know its there to provide support for instance methods because memoized doesnt know what self refers to here, but i dont know how it fixes the problem under the hood ? how does get even get called here ?
