How can i call a Python function from a script that was meant to run on command line

Question

I would like to run this function from a script instead of the command line. For example, the function is:

def main():
    parser = argparse.ArgumentParser(description='Caffe prototxt to mxnet model parameter converter.\
                    Note that only basic functions are implemented. You are welcomed to contribute to this file.')
    parser.add_argument('caffe_prototxt', help='The prototxt file in Caffe format')
    parser.add_argument('caffe_model', help='The binary model parameter file in Caffe format')
    parser.add_argument('save_model_name', help='The name of the output model prefix')
    args = parser.parse_args()
    ...

How can i run it like this?

file.main('file_1.csv', 'file_2.csv', 'name')

And why would someone write a function that I can only run from the command line? It feels inconvenient.

This function is written because it's usually bad to write code under `if name == '__main__'`. — wRAR, Mar 27 '16 at 07:51
Hi @wRAR, do you have any references for me to read up why is it so? Thanks a lot. — kklw, Mar 27 '16 at 07:59
It's simple, you can't call code written under `if name == '__main__'` as easily as code written in a separate function, when you need to call it from a different place. — wRAR, Mar 27 '16 at 08:03
ah. i mean why not just write a function with parameters. eg. def main(file1, file2, name):... @wRAR — kklw, Mar 27 '16 at 09:33
You may want to call `main()` from different scripts etc. OTOH it is a very good idea to separate the actual code that works with parsed arguments to a separate function. — wRAR, Mar 27 '16 at 09:38
What does `main` do with `args`? The part you showed us just parses the command line (something has to do that if it can be run as a script). The real action follows. Does it, for example, pass `args` (or its attributes) to another function? — hpaulj, Mar 27 '16 at 15:53

score 4 · Answer 1 · answered Mar 27 '16 at 07:55

4

You can use sys.argv:

import sys

sys.argv.extend(['file_1.csv', 'file_2.csv', 'name'])
file.main()

answered Mar 27 '16 at 07:55

Mike Müller

82,630
20
166
161

score 0 · Answer 2 · answered Nov 07 '16 at 20:42

You probably want to do a little light re-factoring. Pull the argparse stuff into its own method which then calls main(args), and then instantiate your own argparse.Namespace() that you pass into main with your configuration.

And yes, I agree the code would be better if it was already factored this way. But people code pragmatically to meet their immediate needs.

How can i call a Python function from a script that was meant to run on command line

2 Answers2