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):

try:

return self.cache[args]

except KeyError:

value = self.func(*args)

self.cache[args] = value

return value

except TypeError:

# uncachable -- for instance, passing a list as an argument.

# Better to not cache than to blow up entirely.

return self.func(*args)

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)