import time

def foo():
    time.sleep(2)

def test_swapper(func):
    time_start = time.time()
    func()
    time_end = time.time()
    print('函数执行时间：%s' %(time_end - time_start))

test_swapper(foo)　　# 修改了函数的调用方式 foo()

'''
函数执行时间：2.0000498294830322
'''

import time

def foo():
    time.sleep(2)
    print('from foo...')

def test_swapper(func):
    time_start = time.time()
    func()
    time_end = time.time()
    print('函数执行时间：%s' %(time_end - time_start))
    return func

foo = test_swapper(foo)
foo()
'''
from foo...
函数执行时间：2.0009238719940186
from foo... # 多执行了一次
'''