[Errno 22] Invalid argument

[Larz60+]

Use something like:

import argparse

def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("-i", "--ifile",
                        dest='original_filename',
                        help="Filename where headers are to be replaced",
                        action="store")

    parser.add_argument("-b", "--bfile",
                        dest='replace_original_filename',
                        help="Filename containing body",
                        action="store")

    parser.add_argument("-o", "--ofile",
                        dest='out_filename',
                        help="Output filename",
                        action="store")

    args = parser.parse_args()

    print('original_filename: {}'.format(args.original_filename))
    print('replace_original_filename: {}'.format(args.replace_original_filename))
    print('out_filename: {}'.format(args.out_filename))


if __name__ == '__main__':
    main()

test from command line with:

python TestArgs.py -i 'Myinput1.txt' -b 'MyInput2.txt' -o 'Myoutput.txt'

results:

Output:
λ python TestArgs.py -i 'Myinput1.txt' -b 'MyInput2.txt' -o 'Myoutput.txt'
original_filename: 'Myinput1.txt'
replace_original_filename: 'MyInput2.txt'
out_filename: 'Myoutput.txt'

or with help (-h):

Output:
λ python TestArgs.py -h
usage: TestArgs.py [-h] [-i ORIGINAL_FILENAME] [-b REPLACE_ORIGINAL_FILENAME]
                   [-o OUT_FILENAME]

optional arguments:
  -h, --help            show this help message and exit
  -i ORIGINAL_FILENAME, --ifile ORIGINAL_FILENAME
                        Filename where headers are to be replaced
  -b REPLACE_ORIGINAL_FILENAME, --bfile REPLACE_ORIGINAL_FILENAME
                        Filename containing body
  -o OUT_FILENAME, --ofile OUT_FILENAME
                        Output filename