Decorator__.py

from functools import wraps


def memoize(fn):
    known = dict()

    @wraps(fn)
    def memoizer(*args):
        if args not in known:
            known[args] = fn(*args)
        return known[args]
    return memoizer


@memoize
def nsum(n):
    '''返回前n个数字的和'''
    assert(n >= 0), 'n must be <= 0'
    return 0 if n == 0 else n + nsum(n - 1)


@memoize
def fibonacci(n):
    '''返回斐波那契数列的第n个数'''
    assert(n >= 0), 'n must be >= 0'
    return n if n in (0, 1) else fibonacci(n - 1) + fibonacci(n - 2)

if __name__ == '__main__':
    from timeit import Timer
    measure = [{'exec': 'fibonacci(100)', 'import': 'fibonacci', 'func': fibonacci}, {
        'exec': 'nsum(200)', 'import': 'nsum', 'func': nsum}]
    for m in measure:
        t = Timer(
            '{}'.format(
                m['exec']), 'from __main__ import {}'.format(
                m['import']))
        print('name: {}, doc: {}, executing: {}, time: {}'.format(
            m['func'].__name__, m['func'].__doc__, m['exec'], t.timeit()))