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
