python argparse positional with choices code example
Example 1: python argparse file argument
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('file', type=argparse.FileType('r'))
args = parser.parse_args()
print(args.file.readlines())
Example 2: argparse accept only few options
...
parser.add_argument('--val',
choices=['a', 'b', 'c'],
help='Special testing value')
args = parser.parse_args(sys.argv[1:])