python协程的作用

import time
#遇到IO切换（gevent） + 保存状态
from gevent import monkey  #猴子补丁
monkey.patch_all()  #监听所有的任务是否有IO操作
from gevent import spawn  #spawn(任务)
from gevent import joinall
 
COUNT = 10000000
start = time.clock()
def countdown(n):
    while n > 0:
        n -= 1
 
sp1 = spawn(countdown, COUNT//2)
sp2 = spawn(countdown, COUNT//2)
 
# sp1.start()
# sp2.start()
# sp1.join()
# sp2.join()
joinall([sp1, sp2])  #等同于上面六步
 
print('Time used:', time.clock() - start)
# ('Time used:', 0.40398999999999985)