Documentation

• Introduction to argparse
  • Adding arguments
  • Parsing arguments
• argparse vs. optparse
  • Advantages of argparse
  • Upgrading optparse code
• API documentation
  • ArgumentParser objects
  • The add_argument() method
  • The parse_args() method
  • Other methods
  • Other utilities

Example usage

The following simple example uses the argparse module to generate the command-line interface for a Python program that sums its command-line arguments and writes them to a log file:

import argparse
import sys

if __name__ == '__main__':

    # create the parser
    parser = argparse.ArgumentParser(
        description='Sum the integers on the command line.')

    # add the arguments
    parser.add_argument(
        'integers', metavar='int', type=int, nargs='+',
        help='one of the integers to be summed')
    parser.add_argument(
        '--log', type=argparse.FileType('w'), default=sys.stdout,
        help='the file where the sum should be written '
             '(default: write the sum to stdout)')

    # parse the command line
    args = parser.parse_args()

    # write out the sum
    args.log.write('%s\n' % sum(args.integers))
    args.log.close()

Assuming the Python code above is saved into a file called scriptname.py, it can be run at the command line and provides useful help messages:

$ scriptname.py -h
usage: scriptname.py [-h] [--log LOG] int [int ...]

Sum the integers on the command line.

positional arguments:
  int         one of the integers to be summed

optional arguments:
  -h, --help  show this help message and exit
  --log LOG   the file where the sum should be written (default: write the sum
              to stdout)

When run with the appropriate arguments, it writes the sum of the command-line integers to the specified log file:

$ scriptname.py --log=log.txt 1 1 2 3 5 8
$ more log.txt
20