New submission from Novimir Pablant :
I am trying to get the output from an external program into python using
`subprocess.Popen` and `select.select`. For some reason though select.select
is at times telling me that stdout is not ready to read, even when it is
(reading from it works).
This problem exists in python 3.1 & 3.2 but not in python 2.7.
For my particular application I am connecting to external program via ssh. I
would not expect that the ssh connection would be an issue.
The program that I am calling produces some output and eventually asks for user
input. In the example below I only get a portion of the output, then at some
point select.select tells me that read is not available. If I try to read
anyway I can keep getting more output. As soon as I press a key (passing
something to stdin), select.select tells me that I can read again and I get
the rest of the output.
Any ideas?
def wrapExternal(host=None):
command = ["ssh", "-t", host, "some_program"]
child = subprocess.Popen(command
,bufsize=0
,stdout=subprocess.PIPE
,stderr=subprocess.STDOUT)
out = ''
while True:
r, w, x = select.select([child.stdout], [], [], 1.0)
if child.poll() is not None:
break
if r:
out = child.stdout.read(1)
print(out.decode(), end='')
sys.stdout.flush()
return child.returncode
--
components: Library (Lib)
messages: 130488
nosy: amicitas
priority: normal
severity: normal
status: open
title: Python select.select does not correctly report read readyness
type: behavior
versions: Python 3.1, Python 3.2
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<http://bugs.python.org/issue11459>
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