python协程之解释async关键字原理

目标

解释async关键字原理, 同时举例说明协程中断, 并交出控制权

例子说明

跟yield from的实现一样, 每一行程序都是按顺序一步一步执行的，如果有程序不是按顺序执行，表示曾经交出了控制权，以下的例子，本来应该应该顺序输出1,2，但是因为req1交出了控制权，所以，输出了2,1

import time
from collections import deque

from asynciox.taskx import sleep

_delay = deque()


def sleep1():
def sleep01():
yield
return None
co = sleep01.__code__
sleep01.__code__ = co.replace(co_flags=co.co_flags | 0x100)
return sleep01()


def coroutine(func):
co = func.__code__
func.__code__ = co.replace(co_flags=co.co_flags | 0x100)
return func


@coroutine
def sleep0():
'''
装饰器@：可以理解为 sleep0=coroutine(sleep0),意思就是sleep0函数执行之前，
先调用coroutine方法执行一段内容之后，再把sleep0返回来
'''
yield
return None


async def req1():
b = await sleep0()
return 1


async def req2():
return 2


f1 = req1()
try:
result = f1.send(None)
except StopIteration as e:
print(f'正常打印 {e.value}')
pass
else:
_delay.append((f1, 1+time.time()))

f = req2()
try:
f.send(None)
except StopIteration as e:
print(f'正常打印 {e.value}')
pass

for i, v in _delay:
start = v
while True:
end = time.time()
if start < end:
try:
result = i.send(None)
except StopIteration as e:
print(f'延迟打印 {e.value}')
pass
break
pass

'''
结果:
正常打印 2
延迟打印 1
'''


审核编辑：刘清