I'm using 2 separate scripts, Scale1.py and Scale2.py. To run them I enter sudo python Scale1.py or sudo python Scale2.py from the terminal command line. I would like to have a line in the Scale2.py script in which if I press a button, the program breaks and runs Scale1.py. Something like this, which doesn't work.

if GPIO.input(23) == False:
    break(sudo python Scale1.py)

3 Answers 3


os.system("sudo python scale1.py")

first you will need to import the os module

import os

I don't have a pi with me atm to test, but this comes from the second answer to this question: https://stackoverflow.com/questions/89228/calling-an-external-command-in-python

  • This is what I tried and it worked, thanks a lot Harry! But I did have to combine both programs first. Now the os.system("sudo python Scale3.py") simply restarts at the beginning of Scale3.py program, which is fine. I think import Scale3.py will also work. I didn't try subprocess, it does look interesting and is probably something I need to learn.
    – Rico
    Commented May 25, 2014 at 20:26
  • os.system() has been depricated in favor of subprocess, see stackoverflow.com/a/4256153/4212158
    – crypdick
    Commented Jun 28, 2018 at 17:30

In general, use the subprocess module


for command line calls.

An example processing the result of a subprocess call;

 result = subprocess.check_output(['sudo','service','mpd','restart'])

Subprocess replaces several older modules and functions, like os.system and os.spawn. It does a good job in sanitizing arguments, so it protects you from shell injection.


Of course to run a second python script there is no need for CLI call, you can import those.

  • I'm trying to learn how to issue commands from within a Python script (see here and here) and having some problems. I wonder if subprocess might be better in my case as well.
    – uhoh
    Commented Mar 14, 2018 at 8:44

You can use sudo as harry sib suggested, but you would have to add the user running the first script to the sudoers file.

The best way to run a python script from another python script is to import it. You should have the logic of your script in a method in the second script:

# Scale2.py
def run():

# Run it only if called from the command line
if __name__ == '__main__':
# Scale1.py
import Scale2

if (GPIO.input(23) == False):
  • 2
    +1, Since python is capable of this, it will be the cleanest answer.
    – LuWi
    Commented May 21, 2014 at 19:35
  • 1
    +1, this is the correct way to do what the OP wants and should probably be the accepted answer.
    – user8894
    Commented May 27, 2014 at 16:10

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