Go ahead.
On Jan 17, 2014 6:32 AM, "Jonathan Slenders" <[email protected]>
wrote:
>
> After having experimented a little more, I think I have a working
> solution, but it requires one line change concerning character devices
> again.
> The stream class didn't work out, because of it requires the input and
> output to be on the same file object, what is not possible anymore in
> Python 3. My solution is to connect_read_pipe.
>
> I know that connect_read/write_pipe was not meant to be used for stdin or
> stdout. But they work really very well here and I don't think there is any
> reason not to allow this usage.
>
>
> class InputProtocol:
> def data_received(self, data):
> pass # Handle input here
>
> output_transport, output_protocol = yield from
> loop.connect_write_pipe(BaseProtocol, os.fdopen(0, 'w'))
> input_transport, input_protocol = yield from
> loop.connect_read_pipe(InputProtocol, sys.stdin)
>
> # Print output
> output_transport.write(b'output bytes')
>
>
> For unix_events._UnixReadPipeTransport, it works. Currently, line 196 in
> that file, we have.
>
> if not (stat.S_ISFIFO(mode) or
> stat.S_ISSOCK(mode) or
> stat.S_ISCHR(mode)):
> raise ValueError("Pipe transport is for pipes/sockets only.")
>
>
> In unix_events._UnixWritePipeTransport, on the other hand, we have:
>
> is_socket = stat.S_ISSOCK(mode)
> is_pipe = stat.S_ISFIFO(mode)
> if not (is_socket or is_pipe):
> raise ValueError("Pipe transport is for pipes/sockets only.")
>
> Probably it's a bug that we don't allow character devices there. Shall I
> go ahead and try to create a patch?
>
>
> Jonathan
>
>
>
> Le vendredi 17 janvier 2014 13:59:15 UTC+1, Jonathan Slenders a écrit :
>>
>> Hi all,
>>
>> Still trying here to use stdin/stdout in the event loop.
>>
>> Guido told me to try using StreamReader and StreamWriter from streams.py.
>> This is nice, but I stumbled upon another problem.
>>
>> The idea is that stdin and stdout are actually exactly the same file. If
>> you make one of those non-blocking, the other becomes non blocking as well.
>> The following proves exactly that they are the same.
>>
>> >>> import os, sys
>> >>> o2 = os.fdopen(sys.stdin.fileno(), 'w')
>> >>> o2.write('hello\n')
>> hello
>> 6
>> >>>
>>
>> As far as I understand, in order to use StreamReader/Writer, we need to
>> have one pipe that supports both read and write operations. The
>> StreamReaderProtocol creates an instance of StreamWriter inside its
>> connection_made, using the same transport.
>>
>> In Python2.7.3, this would be easy. I could do this:
>>
>> >>> import os
>> >>> fd = os.fdopen(0, 'r+')
>> >>>
>>
>> However, in Python 3.3, I can't create such an object:
>>
>> >>> import os
>> >>> os.fdopen(0, 'r+')
>> Traceback (most recent call last):
>> File "<stdin>", line 1, in <module>
>> File "/usr/lib/python3.3/os.py", line 1032, in fdopen
>> return io.open(fd, *args, **kwargs)
>> io.UnsupportedOperation: File or stream is not seekable.
>> >>>
>>
>>
>> My idea was to do this:
>>
>>
>> def connected_cb(reader, writer):
>> pass
>>
>> def factory():
>> reader = StreamReader()
>> protocol = StreamReaderProtocol(reader, connected_cb)
>> return protocol
>>
>> in_and_out = os.fdopen(0, 'r+')
>> yield from loop.connect_read_pipe(factory, in_and_out)
>>
>>
>> However, that doesn't work in Python 3.3 because of the
>> UnsupportedOperation error.
>> Maybe, I will find a workaround to still be able to use the
>> StreamReader/Writer. But right now, I'm not sure whether even this is the
>> right approach.
>>
>> One other question about StreamReaderProtocol.
>> Why is it that we pass in stream_reader, but do we create stream_writer
>> in the connection_made. Can't we create both the reader and writer instance
>> in the connection_made? I don't understand this asymmetry.
>>
>>
>> Cheers,
>>
>> Jonathan
>>
>
