18.5.6. 子进程 ¶

18.5.6.1. Windows event loop ¶

On Windows, the default event loop is SelectorEventLoop which does not support subprocesses. ProactorEventLoop should be used instead. Example to use it on Windows:

import asyncio, sys
if sys.platform == 'win32':
    loop = asyncio.ProactorEventLoop()
    asyncio.set_event_loop(loop)

另请参阅

Available event loops and Platform support .

18.5.6.2. Create a subprocess: high-level API using Process ¶

协程 asyncio. create_subprocess_exec ( *args , stdin=None , stdout=None , stderr=None , loop=None , limit=None , **kwds ) ¶

协程 asyncio. create_subprocess_shell ( cmd , stdin=None , stdout=None , stderr=None , loop=None , limit=None , **kwds ) ¶

使用 AbstractEventLoop.connect_read_pipe() and AbstractEventLoop.connect_write_pipe() methods to connect pipes.

18.5.6.3. Create a subprocess: low-level API using subprocess.Popen ¶

Run subprocesses asynchronously using the subprocess 模块。

协程 AbstractEventLoop. subprocess_exec ( protocol_factory , *args , stdin=subprocess.PIPE , stdout=subprocess.PIPE , stderr=subprocess.PIPE , **kwargs ) ¶

协程 AbstractEventLoop. subprocess_shell ( protocol_factory , cmd , * , stdin=subprocess.PIPE , stdout=subprocess.PIPE , stderr=subprocess.PIPE , **kwargs ) ¶

另请参阅

The AbstractEventLoop.connect_read_pipe() and AbstractEventLoop.connect_write_pipe() 方法。

18.5.6.4. Constants ¶

asyncio.subprocess. PIPE ¶

asyncio.subprocess. STDOUT ¶

asyncio.subprocess. DEVNULL ¶

18.5.6.5. 进程 ¶

class asyncio.subprocess. Process ¶

协程 wait ( ) ¶

协程 communicate ( input=None ) ¶

send_signal ( signal ) ¶

terminate ( ) ¶

kill ( ) ¶

stdin ¶

stdout ¶

stderr ¶

警告

使用 communicate() method rather than .stdin.write , .stdout.read or .stderr.read to avoid deadlocks due to streams pausing reading or writing and blocking the child process.

pid ¶

returncode ¶

18.5.6.6. 子进程和线程 ¶

asyncio supports running subprocesses from different threads, but there are limits:

An event loop must run in the main thread
The child watcher must be instantiated in the main thread, before executing subprocesses from other threads. Call the get_child_watcher() function in the main thread to instantiate the child watcher.

The asyncio.subprocess.Process class is not thread safe.

另请参阅

The asyncio 中的并发和多线程章节。

18.5.6.7. 子进程范例 ¶

18.5.6.7.1. Subprocess using transport and protocol ¶

Example of a subprocess protocol using to get the output of a subprocess and to wait for the subprocess exit. The subprocess is created by the AbstractEventLoop.subprocess_exec() 方法：

import asyncio
import sys
class DateProtocol(asyncio.SubprocessProtocol):
    def __init__(self, exit_future):
        self.exit_future = exit_future
        self.output = bytearray()
    def pipe_data_received(self, fd, data):
        self.output.extend(data)
    def process_exited(self):
        self.exit_future.set_result(True)
@asyncio.coroutine
def get_date(loop):
    code = 'import datetime; print(datetime.datetime.now())'
    exit_future = asyncio.Future(loop=loop)
    # Create the subprocess controlled by the protocol DateProtocol,
    # redirect the standard output into a pipe
    create = loop.subprocess_exec(lambda: DateProtocol(exit_future),
                                  sys.executable, '-c', code,
                                  stdin=None, stderr=None)
    transport, protocol = yield from create
    # Wait for the subprocess exit using the process_exited() method
    # of the protocol
    yield from exit_future
    # Close the stdout pipe
    transport.close()
    # Read the output which was collected by the pipe_data_received()
    # method of the protocol
    data = bytes(protocol.output)
    return data.decode('ascii').rstrip()
if sys.platform == "win32":
    loop = asyncio.ProactorEventLoop()
    asyncio.set_event_loop(loop)
else:
    loop = asyncio.get_event_loop()
date = loop.run_until_complete(get_date(loop))
print("Current date: %s" % date)
loop.close()

18.5.6.7.2. Subprocess using streams ¶

Example using the Process class to control the subprocess and the StreamReader class to read from the standard output. The subprocess is created by the create_subprocess_exec() 函数：

import asyncio.subprocess
import sys
@asyncio.coroutine
def get_date():
    code = 'import datetime; print(datetime.datetime.now())'
    # Create the subprocess, redirect the standard output into a pipe
    create = asyncio.create_subprocess_exec(sys.executable, '-c', code,
                                            stdout=asyncio.subprocess.PIPE)
    proc = yield from create
    # Read one line of output
    data = yield from proc.stdout.readline()
    line = data.decode('ascii').rstrip()
    # Wait for the subprocess exit
    yield from proc.wait()
    return line
if sys.platform == "win32":
    loop = asyncio.ProactorEventLoop()
    asyncio.set_event_loop(loop)
else:
    loop = asyncio.get_event_loop()
date = loop.run_until_complete(get_date())
print("Current date: %s" % date)
loop.close()

18.5.6. 子进程 ¶

18.5.6.1. Windows event loop ¶

18.5.6.2. Create a subprocess: high-level API using Process ¶

18.5.6.3. Create a subprocess: low-level API using subprocess.Popen ¶

18.5.6.4. Constants ¶

18.5.6.5. 进程 ¶

18.5.6.6. 子进程和线程 ¶

18.5.6.7. 子进程范例 ¶

18.5.6.7.1. Subprocess using transport and protocol ¶

18.5.6.7.2. Subprocess using streams ¶

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