In Python, can I call the main() of an imported module?

Martijen's answer makes sense, but it was missing something crucial that may seem obvious to others but was hard for me to figure out.

In the version where you use argparse, you need to have this line in the main body.

args = parser.parse_args(args) 

Normally when you are using argparse just in a script you just write

args = parser.parse_args() 

and parse_args find the arguments from the command line. But in this case the main function does not have access to the command line arguments, so you have to tell argparse what the arguments are.

Here is an example

import argparse import sys def x(x_center, y_center): print "X center:", x_center print "Y center:", y_center def main(args): parser = argparse.ArgumentParser(description="Do something.") parser.add_argument("-x", "--xcenter", type=float, default= 2, required=False) parser.add_argument("-y", "--ycenter", type=float, default= 4, required=False) args = parser.parse_args(args) x(args.xcenter, args.ycenter) if __name__ == '__main__': main(sys.argv[1:]) 

Assuming you named this mytest.py To run it you can either do any of these from the command line

python ./mytest.py -x 8 python ./mytest.py -x 8 -y 2 python ./mytest.py 

which returns respectively

X center: 8.0 Y center: 4 

or

X center: 8.0 Y center: 2.0 

or

X center: 2 Y center: 4 

Or if you want to run from another python script you can do

import mytest mytest.main(["-x","7","-y","6"]) 

which returns

X center: 7.0 Y center: 6.0 

It depends. If the main code is protected by an if as in:

if __name__ == '__main__': ...main code... 

then no, you can't make Python execute that because you can't influence the automatic variable __name__.

But when all the code is in a function, then might be able to. Try

import myModule myModule.main() 

This works even when the module protects itself with a __all__.

from myModule import * might not make main visible to you, so you really need to import the module itself.

The answer I was searching for was answered here: How to use python argparse with args other than sys.argv?

If main.py and parse_args() is written in this way, then the parsing can be done nicely

# main.py import argparse def parse_args(): parser = argparse.ArgumentParser(description="") parser.add_argument('--input', default='my_input.txt') return parser def main(args): print(args.input) if __name__ == "__main__": parser = parse_args() args = parser.parse_args() main(args) 

Then you can call main() and parse arguments with parser.parse_args(['--input', 'foobar.txt']) to it in another python script:

# temp.py from main import main, parse_args parser = parse_args() args = parser.parse_args([]) # note the square bracket # to overwrite default, use parser.parse_args(['--input', 'foobar.txt']) print(args) # Namespace(input='my_input.txt') main(args) 

I had the same need using argparse too. The thing is parse_args function of an argparse.ArgumentParser object instance implicitly takes its arguments by default from sys.args. The work around, following Martijn line, consists of making that explicit, so you can change the arguments you pass to parse_args as desire.

def main(args): # some stuff parser = argparse.ArgumentParser() # some other stuff parsed_args = parser.parse_args(args) # more stuff with the args if __name__ == '__main__': import sys main(sys.argv[1:]) 

The key point is passing args to parse_args function. Later, to use the main, you just do as Martijn tell.

Assuming you are trying to pass the command line arguments as well.

import sys import myModule def main(): # this will just pass all of the system arguments as is myModule.main(*sys.argv) # all the argv but the script name myModule.main(*sys.argv[1:]) 

I hit this problem and I couldn't call a files Main() method because it was decorated with these click options, eg:

# @click.command() # @click.option('--username', '-u', help="Username to use for authentication.") 

When I removed these decorations/attributes I could call the Main() method successfully from another file.

from PyFileNameInSameDirectory import main as task task()