On 3/28/2014 6:20 AM, Victor Stinner wrote:
> Full example of asynchronous communication with a subprocess (the
> python interactive interpreter) using asyncio high-level API:
Thank you for writing this. As I explained in response to Josiah, Idle
communicates with a python interpreter subprocess through a socket.
Since making the connection is not dependable, I would like to replace
the socket with the pipes. http://bugs.python.org/issue18823
However, the code below creates a subprocess for one command and one
response, which can apparently be done now with subprocess.communicate.
What I and others need is a continuing (non-blocking) conversion with 1
and only 1 subprocess (see my response to Josiah), and that is much more
difficult. So this code does not do what he claims his will do.
However it is done, I agree with the intent of the PEP to make it much
easier to talk with a subprocess. Victor, if you can rewrite the below
with a run_forever loop that can accept new write-read task pairs and
also make each line read immediately accessible, that would be really
helpful. Post it on the issue above if you prefer.
Another difference from what you wrote below and what Idle does today is
that the shell, defined in idlelib/PyShell.py, does not talk to the
subprocess interpreter directly but to a run supervisor defined in
idlelib/run.py through an rpc protocol ('cmd', 'arg string'). To use the
pipes, the supervisor would grab all input from stdin (instead of the
socket) and exec user code as it does today, or it could be replaced by
a supervisor class with an instance with a name like
_idle_supervisor_3_4_0_ that would be extremely unlikely to clash with
any name created by users.
> ---
> import asyncio.subprocess
> import time
> import sys
>
> @asyncio.coroutine
> def eval_python_async(command, encoding='ascii', loop=None):
> proc = yield from asyncio.subprocess.create_subprocess_exec(
> sys.executable, "-u", "-i",
> stdin=asyncio.subprocess.PIPE,
> stdout=asyncio.subprocess.PIPE,
> stderr=asyncio.subprocess.STDOUT,
> loop=loop)
>
> # wait for the prompt
> buffer = bytearray()
> while True:
> data = yield from proc.stdout.read(100)
> buffer.extend(data)
> if buffer.endswith(b'>>> '):
> break
>
> proc.stdin.write(command.encode(encoding) + b"\n")
> yield from proc.stdin.drain()
> proc.stdin.close()
>
> output = yield from proc.stdout.read()
>
> output = output.decode(encoding)
> output = output.rstrip()
> if output.endswith('>>>'):
> output = output[:-3].rstrip()
> return output
>
> def eval_python(command, timeout=None):
> loop = asyncio.get_event_loop()
> task = asyncio.Task(eval_python_async(command, loop=loop), loop=loop)
> return loop.run_until_complete(asyncio.wait_for(task, timeout))
>
> def test_sequential(nproc, command):
> t0 = time.monotonic()
> for index in range(nproc):
> eval_python(command)
> return time.monotonic() - t0
>
> def test_parallel(nproc, command):
> loop = asyncio.get_event_loop()
> tasks = [asyncio.Task(eval_python_async(command, loop=loop), loop=loop)
> for index in range(nproc)]
> t0 = time.monotonic()
> loop.run_until_complete(asyncio.wait(tasks))
> return time.monotonic() - t0
>
> print("1+1 = %r" % eval_python("1+1", timeout=1.0))
>
> slow_code = "import math; print(str(math.factorial(20000)).count('7'))"
>
> dt = test_sequential(10, slow_code)
> print("Run 10 tasks in sequence: %.1f sec" % dt)
>
> dt2 = test_parallel(10, slow_code)
> print("Run 10 tasks in parallel: %.1f sec (speed=%.1f)" % (dt2, dt/dt2))
>
> # cleanup asyncio
> asyncio.get_event_loop().close()
--
Terry Jan Reedy
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