cache-decorator.py

#Recipe 325205: Cache decorator in python 2.4
#http://code.activestate.com/recipes/325205/, http://www.python.org/peps/pep-0318.html

def memoize(f, cache={}):
    def g(*args, **kwargs):
        key = ( f, tuple(args), frozenset(kwargs.items()) )
        if key not in cache:
            cache[key] = f(*args, **kwargs)
        return cache[key]
    return g


def safecall(f, default=None, exception=Exception):
    '''Returns modified f. When the modified f is called and throws an
    exception, the default value is returned'''
    def _safecall(*args,**argv):
        try:
            return f(*args,**argv)
        except exception:
            return default
    return _safecall

#[safecall(int)(i) for i in '1 2 x'.split()]   # returns [1, 2, None]
#[safecall(int, -1, ValueError)(i) for i in '1 2 x'.split()]    # returns [1, 2, -1]


if __name__ == '__main__':
    @memoize
    def f(n):
        return (n<=2) and 1 or (f(n-1)+f(n-2))

    f(40) # blindingly fast