python如何获取程序执行时间?

import time

start =time.clock()

#中间写上代码块

end = time.clock()

print('Running time: %s Seconds'%(end-start))

import time

start=time.time()

#中间写上代码块

end=time.time()

print('Running time: %s Seconds'%(end-start))

import datetime

start=datetime.datetime.now()

#中间写代码块

end=datetime.datetime.now()

print('Running time: %s Seconds'%(end-start))