asyncio标准库6 Threads & Subprocess

Threads

import asyncio

def compute_pi(digits):

    # implementation

    return 3.14

async def main(loop):

    digits = await loop.run_in_executor(None, compute_pi, 20000)

    print("pi: %s" % digits)

loop = asyncio.get_event_loop()

loop.run_until_complete(main(loop))

loop.close()

# AbstractEventLoop.run_in_executor(executor, func, *args)

#  Executor (pool of threads or pool of processes)

Subprocess

Run a subprocess and read its output

import asyncio

async def run_command(*args):

    # Create subprocess

    process = await asyncio.create_subprocess_exec(

        *args,

        # stdout must a pipe to be accessible as process.stdout

        stdout=asyncio.subprocess.PIPE)

    # Wait for the subprocess to finish

    stdout, stderr = await process.communicate()

    # Return stdout

    return stdout.decode().strip()

loop = asyncio.get_event_loop()

# Gather uname and date commands

commands = asyncio.gather(run_command('uname'), run_command('date'))

# Run the commands

uname, date = loop.run_until_complete(commands)

# Print a report

print('uname: {}, date: {}'.format(uname, date))

loop.close()

Communicate with a subprocess using standard streams

import asyncio

async def echo(msg):

    # Run an echo subprocess

    process = await asyncio.create_subprocess_exec(

        'cat',

        # stdin must a pipe to be accessible as process.stdin

        stdin=asyncio.subprocess.PIPE,

        # stdout must a pipe to be accessible as process.stdout

        stdout=asyncio.subprocess.PIPE)

    # Write message

    print('Writing {!r} ...'.format(msg))

    process.stdin.write(msg.encode() + b'\n')

    # Read reply

    data = await process.stdout.readline()

    reply = data.decode().strip()

    print('Received {!r}'.format(reply))

    # Stop the subprocess

    process.terminate()

    code = await process.wait()

    print('Terminated with code {}'.format(code))

loop = asyncio.get_event_loop()

loop.run_until_complete(echo('hello!'))

loop.close()