Subprocess Popen confusion
Dick Holmes
encore1 at cox.net
Wed May 13 23:13:57 EDT 2020
https://occovid19.ochealthinfo.com/coronavirus-in-oc I'm trying to
communicate using a continuing dialog between two
processes on the same system. I've looked at various mechanisms and the
class that seems to fit my needs is Popen in the subprocess module, but
I can't seem to get more than a single round-trip message through Popen.
I first call Popen then poll using the identifier returned from the call
and the poll seems to work. I then call the communicate function passing
None as the value to send to the companion process stdin. I get the
expected result, but I also get "Exception condition detected on fd 0
\\n" and "error detected on stdin\\n". Subsequent attempts to
read/write/communicate with the subprocess fail because the file (stdxx
PIPE) is closed.
I can't tell from the documentation if the communicate function is a
one-time operation. I have tried using read but the read call doesn't
return (I'm using winpdb-reborn to monitor the operations).
I'm using Python 3.7, Windows 10, winpdb-reborn 2.0.0, rpdb2 1.5.0. If
it makes any difference, I'm trying to communicate with GDB using the MI
interpreter.
Thoughts and advice appreciated!
Dick
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