Python Asyncio子进程永远不会完成

Question

我有一个简单的python程序,我用它来测试子进程的asyncio:

import sys, time
for x in range(100):
    print("processing (%s/100)    " % x)
    sys.stdout.flush()
print("enjoy")
sys.stdout.flush()

在命令行上运行它会产生所需的结果.

但是,从asyncio调用时,它永远不会完成

process = yield from asyncio.create_subprocess_exec(
    *["python", "program.py"],
    stdout=async_subprocess.PIPE,
    stderr=async_subprocess.STDOUT,
    cwd=working_dir
)

# this never finishes
yield from process.communicate()

ps ax显示这个过程<defunct>,不确定这意味着什么

Answer 1

我怀疑你的问题只是涉及到你是如何调用 asyncio.create_subprocess_exec和process.communiate().这个完整的例子适合我:

import asyncio
from asyncio import subprocess

@asyncio.coroutine
def do_work():
    process = yield from asyncio.create_subprocess_exec(
        *["python", "program.py"],
        stdout=subprocess.PIPE,
        stderr=subprocess.STDOUT
    )

    stdout, _= yield from process.communicate()
    print(stdout)

if __name__  == "__main__":
    loop = asyncio.get_event_loop()
    loop.run_until_complete(do_work())

您必须放置yield from在a内部使用的代码,asyncio.coroutine然后在事件循环(使用loop.run_until_complete)中调用它,以使其按照您希望的方式运行.