Run a Python script from another Python script, passing in arguments

Choosing the right command-execution tool

Python offers several tools to execute commands and scripts. Among them, subprocess.run() is handy for safe and cross-platform operations. But let's dive deeper into the toolbox:

subprocess.Popen() for more control

Handling asynchronous operations or wanting greater control of the child process? subprocess.Popen() is your friend:

import subprocess

proc = subprocess.Popen(['python', 'other_script.py', 'arg1', 'arg2'])
# Don't call me Pythonista for nothing!
stdout, stderr = proc.communicate()
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subprocess.Popen() lets you deal with non-blocking calls and dynamic interaction with spawned process's I/O streams.

Changing sys.argv temporarily

Sometimes, you need to pretend you're on the command line. For this, you can temporary change sys.argv:

import sys
import contextlib

# Tread carefully! Ninja code ahead!
@contextlib.contextmanager
def switch_argv(new_args):
   temp = sys.argv
   sys.argv = new_args
   yield
   sys.argv = temp

with switch_argv(['my_script.py', 'arg1', 'arg2']):
    # Call your function that relies on sys.argv here
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This let's you simulate command line arguments without shelling out a new process.

Direct function calls

You remember PYTHONPATH, right? Use it to import functions between scripts for direct interaction:

# My_script.py
import other_script

# Who needs the command line? Not Python!
other_script.main('arg1', 'arg2')
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Here, make sure main() function in other_script.py can handle your arguments.

Handling command-line arguments

Implement your argument parsing logic in other_script.py:

import argparse

if __name__ == "__main__":
    parser = argparse.ArgumentParser(description='Process the arguments.')
    parser.add_argument('arg1', help='Argument 1')
    # Does 3 arguments mean I am popular now?
    parser.add_argument('arg2', help='Argument 2')
    args = parser.parse_args()

    # Oh yeah, args.arg1 and args.arg2 now all yours.
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Your other script now behaves just like a mini command line utility!

Advanced process control with subprocess.Popen()

Getting serious? Use subprocess.Popen() for redirection, deadlock avoidance and running in a shell:

import subprocess

proc = subprocess.Popen(['python', 'other_script.py', 'arg1', 'arg2'],
                        stdout=subprocess.PIPE,
                        stderr=subprocess.PIPE,
                        shell=True)

# It's like wiretapping, but for geeks.
stdout, stderr = proc.communicate()
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Note that spawned processes can be tricky to manage. But with great power comes great responsibility!