所以我有一个倒计时脚本,如下所示:
import time, threading, asyncio
def countdown(n, m):
print("timer start")
time.sleep(n)
print("timer stop")
yield coro1
async def coro1():
print("coroutine called")
async def coromain():
print("first")
t1 = threading.Thread(target=countdown, args=(5, 0))
t1.start()
print("second")
loop = asyncio.get_event_loop()
loop.run_until_complete(coromain())
loop.stop()
我想要它做的很简单:
Run coromain
Print "first"
Start thread t1, print "timer start" and have it wait for 5 seconds
In the mean time, print "second"
after 5 seconds, print "timer stop"
exit
但是,当我运行此代码时,它会输出:
Run coromain
Print "first"
Print "second"
exit
我很困惑为什么要这样做。谁能解释一下我在这里做错了什么?
最佳答案
这取决于您的问题是否是施加额外约束的更大问题的一部分,但我不认为有理由使用线程
。相反,您可以使用在同一事件循环中运行的两个单独的任务,这是异步编程的要点之一:
import asyncio
async def countdown(n, m): # <- coroutine function
print("timer start")
await asyncio.sleep(n)
print("timer stop")
await coro1()
async def coro1():
print("coroutine called")
async def coromain():
print("first")
asyncio.ensure_future(countdown(5, 0)) # create a new Task
print("second")
loop = asyncio.get_event_loop()
loop.run_until_complete(coromain()) # run coromain() from sync code
pending = asyncio.Task.all_tasks() # get all pending tasks
loop.run_until_complete(asyncio.gather(*pending)) # wait for tasks to finish normally
输出:
first
second
timer start
(5 second wait)
timer stop
coroutine called
当使用ensure_future
时,您可以在单个操作系统的线程内有效地创建一个新的“执行线程”(请参阅纤程)。
关于Python 从普通函数调用协程,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/48993459/