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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)
Aurora0001
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Rico
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3 Answers3

26

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

Community
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mrwhale
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  • 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 May 25 '14 at 20:26
  • os.system() has been depricated in favor of subprocess, see https://stackoverflow.com/a/4256153/4212158 – crypdick Jun 28 '18 at 17:30
12

In general, use the subprocess module

subprocess.call(["sudo","python","scale1.py"])

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.

https://docs.python.org/2/library/subprocess.html

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

Janghou
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  • 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 Mar 14 '18 at 08:44
6

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():
    do_first()
    do_second()
    [...]

# Run it only if called from the command line
if __name__ == '__main__':
    run()

# Scale1.py
import Scale2

if (GPIO.input(23) == False):
    Scale2.run()
Gagaro
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    +1, Since python is capable of this, it will be the cleanest answer. – LuWi May 21 '14 at 19:35
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    +1, this is the correct way to do what the OP wants and should probably be the accepted answer. –  May 27 '14 at 16:10