How to run python script from command line or from another script

Question

I downloaded a script written in Python, called let's say 'myScript.py', but I don't know how to run it. It has the following structure:

import numpy as np
import argparse
parser = argparse.ArgumentParser(description='manual to this script')
parser.add_argument('--file', type=str, default = None)
parser.add_argument('--timeCor', type=bool, default = False)
parser.add_argument('--iteration', type=str, default = 'Newton')
args = parser.parse_args()
def func1(file):
...
def func2(file):
...
def calculate(data, timeCor=False, iteration='Newton'):
...
if __name__ == "__main__":
 print('\n--- Calculating ---\nN file:',args.file)
 print('Time correction =',args.timeCor,
 '\nIteration strategy =',args.iteration,'\n')
 
 rawdata,data = func2(args.file)
 pos = calculate(data,timeCor=args.timeCor,iteration=args.iteration)
 for each in pos:
 print('Pos:',format(np.uint8(each[0]),'2d'),each[1:-1])
 np.savetxt('pos.csv',pos,delimiter=',')
 print('--- Save file as "pos.csv" in the current directory ---')

How can I run it from command line? And from another script? Thank you in advance!

Answer 1

If I understood your question correctly, you are asking about executing this python program from another python script. This can be done by making use of subprocess.

import subprocess
process = subprocess.run(["python3", "path-to-myScript.py", "command line arguments here"], capture_output=True)
output = process.stdout.decode() # stdout is bytes
print(output)

If you do not want to provide the command in a list, you can add shell=True as an argument to subprocess.run(), or you can use shlex.split().

If you are on windows, replace python3 with python.

However this solution is not very portable, and on a more general note, if you are not strictly needing to run the script, I would recommend you to import it and call its functions directly instead.

To run the python script from command line:

python myScript.py --arguments

And as @treuss has said, if you are on a Unix system (macOS or Linux) you can add a shebang to the top of the script, but I recommend to use the following instead:

#!/usr/bin/env python3

for portability sake, as the actual path of python3 may vary.

To run the edited program:

chmod +x myScript # to make file executable, and note that there is no longer a .py extension as it is not necessary
./myScript --arguments

• eljamba: Thank you for your explanationi. However if I try to execute from command line, I get the following error: SyntaxError: invalid syntax, TypeError: object NoneType can't be used in 'await' expression I tried both the following: python myScript.py --file="fileName.fileExtension"
• Brandon Li: @eljamba did you get the error from running myScript.py or running the other script that is running myScript.py using subprocess?
• eljamba: the first one you said, I tried python myScript.py --file="fileName.fileExt" and the same command with python3 instead
• Brandon Li: That would be an issue with the script itself. Maybe you can post a separate question regarding this issue.

Answer 2

Run it by executing:

python myScript.py

Alternatively, on systems which support it (UNIX-Like systems), you can add what's called a she-bang to the first line of the file:

#!/usr/bin/python

Note that /usr/bin/python should be the actual path where your python is located. After that, make the file executable:

chmod u+x myScript.py

and run it either from the current directory:

./myScript.py

or from a different directory with full or relative path:

/path/to/python/scripts/myScript.py