python 的装饰器解释

装饰器：

import time
def timeit(fn):
    def wrap(*args,**kwargs):
        start = time.time()
        fn(*args,**kwargs)
        print (time.time() - start)
    return wrap
    
def sleep(x):
    time.sleep(x)

timeit(sleep)(3)
3.003286123275757


@timeit
def sleep(x):
    time.sleep(x)

sleep(2)


2.00276517868042

分解开就是:
fn  = timeit(sleep)
fn(3)

3.00378155708313