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subprocess

module

Run external programs: pass arguments, get the exit code, capture stdout and stderr.

Syntax

import subprocess

subprocess.run is almost always enough; Popen is for talking to a process while it runs. Pass the command as a list of arguments — shell=True with a string built from user input opens command injection. A non-zero exit code is not an error by itself: you get an exception only with check=True. The module replaces os.system and os.popen.

Examples

import subprocess, sys
r = subprocess.run([sys.executable, '-c', 'print("hi")'], capture_output=True, text=True)
print(r.returncode, r.stdout.strip())  # → 0 hi

See also

Common errors

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