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Editorial Team
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Asked: 2026-06-08T07:35:05+00:00

On Windows I have a program (prog.exe) that reads from stdin. In python I

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On Windows I have a program (prog.exe) that reads from stdin. In python I want to pipe a string as the input to its stdin. How to do that?

Something like:

subprocess.check_output("echo {0} | myprog.exe".format(mystring))

or (to make the args a list)

subprocess.check_output("echo {0} | myprog.exe".format(mystring).split())

doesn’t seem to work. It gave me:

WindowsError: [Error 2] The system cannot find the file specified

I also tried to use the “stdin” keyword arg with StringIO (which is a file-like object)

subprocess.check_output(["myprog.exe"], stdin=StringIO(mystring))

Still no luck – check_output doesn’t work with StringIO.

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1 Answer

  1. Editorial Team

    You should use Popen communicate method (docs). 

    proc = subprocess.Popen(["myprog.exe"], stdin=subprocess.PIPE)
stdout, stderr = proc.communicate('my input')
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