How do you call a python file that requires a command line argument from within another python file?

Question

For example, I have two python files, 'test1.py' and 'test2.py'. I want to import test2 into test1, so that when I run test1, it also runs test2.

However, in order to run properly, test2 requires an input argument. Normally when I run test2 from outside of test1, I just type the argument after the file call in the command line. How do I accomplish this when calling test2 from within test1?

• jonrsharpe: Without knowing how test2 is structured, it's very difficult to say. If whoever wrote it factored the argument parsing into a separate function and/or used if __name__ == '__main__' properly, you can likely just bypass it and inject your parameter straight in. If not, you may have to fiddle with sys.argv.

Answer 1

Depending on the ability of editing test2.py there are two options:

1. (Possible to edit) Pack test2.py content into class and pass args in init.

in test1.py file:

from test2 import test2class
t2c = test2class(neededArgumetGoHere)
t2c.main()

in test2.py file:

class test2class:
 def __init__(self, neededArgumetGoHere):
 self.myNeededArgument = neededArgumetGoHere
 def main(self):
 # do stuff here
 pass
# to run it from console like a simple script use
if __name__ == "__main__":
 t2c = test2class(neededArgumetGoHere)
 t2c.main()

2. (Not possible to edit test2.py) Run test2.py as a subprocess. Check subprocess docs for more info how to use it.

test1.py

from subprocess import call
call(['path/to/python','test2.py','neededArgumetGoHere'])

Answer 2

Assuming you can define your own test1 and test2 and that you are OK with using argparse (which is a good idea anyway):

The nice thing with using argparse is that you can let test2 define a whole bunch of default parameter values that test1 doesn't have to worry about. And, in a way, you have a documented interface for test2's calling.

Cribbed off https://docs.python.org/2/howto/argparse.html

test2.py

import argparse
def get_parser():
 "separate out parser definition in its own function"
 parser = argparse.ArgumentParser()
 parser.add_argument("square", help="display a square of a given number")
 return parser
def main(args):
 "define a main as the test1=>test2 entry point"
 print (int(args.square)**2)
if __name__ == '__main__':
 "standard test2 from command line call"
 parser = get_parser()
 args = parser.parse_args()
 main(args)

audrey:explore jluc$ python test2.py 3

9

test1.py

import test2
import sys
#ask test2 for its parser
parser = test2.get_parser()
try:
 #you can use sys.argv here if you want
 square = sys.argv[1]
except IndexError:
 #argparse expects strings, not int
 square = "5"
#parse the args for test2 based on what test1 wants to do
#by default parse_args uses sys.argv, but you can provide a list
#of strings yourself.
args = parser.parse_args([square])
#call test2 with the parsed args
test2.main(args)

audrey:explore jluc$ python test1.py 6

36

audrey:explore jluc$ python test1.py

25

Answer 3

You can use the call or popen method from subprocess module.

from subprocess import call, Popen
Call(file, args)
Popen(file args)