自定义计时器with

import time

class M_TimeCounter():
    def __init__(self,prefix=None):
        self.prefix=prefix+' ' if prefix else ' '

    def __enter__(self):
        self.start=time.time()

    def __exit__(self, exc_type, exc_val, exc_tb):
        print('%stime: %.4f sec' %(self.prefix,time.time()-self.start))

def run(x):
    for _ in range(x):
        y=100/10

with M_TimeCounter():
    run(1000000)