Python popen python.exe

Question

I'm rather puzzled by why the code below doesn't print stdout and exit, instead it hangs (on windows). Any reason why?

import subprocess
from subprocess import Popen

def main():
    proc = Popen(
        'C:/Python33/python.exe',
        stderr=subprocess.STDOUT,
        stdin=subprocess.PIPE,
        stdout=subprocess.PIPE
    )
    proc.stdin.write(b'exit()\r\n')
    proc.stdin.flush()
    print(proc.stdout.read(1))

if __name__=='__main__':
    main()

Answer 1

Replace the following:

proc.stdin.flush()

with:

proc.stdin.close()

Otherwise the subprocess python.exe will wait forever stdin to be closed.

---

Alternative: using communicate()

proc = Popen(...)
out, err = proc.communicate(b'exit()\r\n')
print(out)  # OR print(out[:1]) if you want only the first byte to be print.