gistfile1.py

import functools

class CallableCache(object):
    def __init__(self, cache=None):
        self._cache = cache or {}
    
    def __call__(self, fn):
        def w(*args, **kwargs):
            try:
                key = hash((fn, args, tuple(kwargs.items())))
            except TypeError, e: # non cacheable call
                out = fn(*args, **kwargs)
            else:
                if key in self._cache:
                    return self._cache[key]
                out = fn(*args, **kwargs)
                self._cache[key] = out
            return out
        return functools.wraps(fn)(w)

callable_cache = CallableCache()

# usage:
# @callable_cache
# def f(foo, bar):
#     ...