It's funny that I've been using subprocesses without even being aware of
loop.subprocess_exec(). I just followed the child_process.py example in
Tulip, and it works fine. Why should we use loop.subprocess_xxx instead of
plain old subprocess.Popen followed by connecting the pipes to asyncio
streams?
On 23 January 2014 16:17, Phil Schaf <trueflyingsh...@gmail.com> wrote:
> Am Donnerstag, 23. Januar 2014 16:48:46 UTC+1 schrieb Guido van Rossum:
>
> Read the source code of asyncio/streams.py. There are helper classes
>> that should let you do it. Please post the solution here.
>> --
>> --Guido van Rossum (python.org/~guido)
>>
> i’m deep inside that source for some hours now, but since i never did
> multiple inheritance, only your comment convinced me that i can ideed marry
> SubprocessProtocol and a StreamReaderProtocol.
>
> import sysfrom functools import partialfrom asyncio.protocols import
> SubprocessProtocolfrom asyncio.streams import StreamReader,
> StreamReaderProtocol
>
> cmd = […]
> @coroutinedef do_task(msg):
> loop = get_event_loop()
> reader = StreamReader(float('inf'), loop)
>
> transport, proto = yield from loop.subprocess_exec(
> partial(StdOutReaderProtocol, reader, loop=loop), *cmd)
>
> stdin = transport.get_pipe_transport(0)
> stdin.write(msg)
> stdin.write_eof() # which of those is actually necessary? only eof? only
> close?
> stdin.close()
>
> while True: # would be nice to do “for line in iter(reader.readline,
> b'')”, but not possible with coroutines
> line = yield from reader.readline()
> if not line:
> break
> do_something_with(line)
> class StdOutReaderProtocol(StreamReaderProtocol, SubprocessProtocol):
> def pipe_data_received(self, fd, data):
> if fd == 1:
> self.data_received(data)
> else:
> print('stderr from subprocess:', data.decode(), file=sys.stderr,
> end='')
>
> that was completely strange, though. imho there should be a easier way to
> do it instead of figuring this one out.
>
> thanks for your encouragement!
>
> – Phil
>
--
Gustavo J. A. M. Carneiro
Gambit Research LLC
"The universe is always one step beyond logic." -- Frank Herbert
