python pipe only stdin,out once, how to do twice or more time

问题

success python pipe stdin, out only one time this source

main.py

import subprocess from subprocess import PIPE, STDOUT

player_pipe = subprocess.Popen(["source\call.py", 'arg1'], stdin=PIPE,
     stdout=PIPE, stderr=STDOUT, shell=True)

player_pipe.stdin.write("Send Msg\n")
get_stdout = player_pipe.stdout.readline()
print("[Get Msg]" + get_stdout)

player_pipe.kill()
player_pipe.wait()

call.py

import sys

getMsg = raw_input()
print getMsg

but I want twice or more time stdin, out

so update source but it's not work

What's wrong this source

main.py (update-not work)

import subprocess from subprocess import PIPE, STDOUT

player_pipe = subprocess.Popen(["source\call.py", 'arg1'], stdin=PIPE,
     stdout=PIPE, stderr=STDOUT, shell=True)

player_pipe.stdin.write("Send Msg\n")
get_stdout = player_pipe.stdout.readline()
print("[Get Msg]" + get_stdout)

player_pipe.stdin.write("Send Msg2\n")
get_stdout = player_pipe.stdout.readline()
print("[Get Msg]" + get_stdout)

player_pipe.kill()
player_pipe.wait()

call.py(update-not work)

import sys

getMsg = raw_input()
print getMsg

getMsg2 = raw_input()
print getMsg2

回答1:

the output of call.py is buffered. so you have to flush() it to send to main.py.

#!/usr/bin/python2
import sys

getMsg = raw_input()
print getMsg
sys.stdout.flush()

getMsg2 = raw_input()
print getMsg2
sys.stdout.flush()

Note that you need shebang #!/usr/bin/python2 at least when your OS is Linux (I don't know why OP's code works without shebang. Maybe some Windows magic ?).

Also you can use -u option not to buffer the output of python.

player_pipe = subprocess.Popen(["/usr/bin/python2","-u","./call.py"], stdin=PIPE,
     stdout=PIPE, stderr=STDOUT, shell=False)

回答2:

When you say "but I want twice or more time stdin, out", I'm not sure what you really mean.

In a basic Linux/UNIX system, you have 1 - and only one - STDIN, STDOUT, and STDERR. Now, you can pipe things in and out, treating STDERR separately if you want, but you cannot just arbitrarily assign multiple inputs without setting up separate mechanisms (sockets, etc) to handle that within your program.

来源：https://stackoverflow.com/questions/41628070/python-pipe-only-stdin-out-once-how-to-do-twice-or-more-time

标签

python

pipeline