Argparse: Way to include default values in '--help'?

Last Updated : 19 Jun, 2024

Argparse in Python allows you to create user-friendly command-line interfaces. By including default values in the --help output, you can make your script's behavior more transparent. There are several ways to achieve this, including using argparse.ArgumentDefaultsHelpFormatter and custom help formatters.

Include default values in '--help'

Below are the ways to include default values in '--help' in Python.

Using argparse.ArgumentDefaultsHelpFormatter
Using Custom Help Formatter

Include default values in '--help' Using argparse.ArgumentDefaultsHelpFormatter

In this example, we are using argparse.ArgumentDefaultsHelpFormatter to automatically include the default values of the arguments in the --help output. This makes it clear to users what the defaults are for --course, --duration, and --level options.

Python

import argparse
parser = argparse.ArgumentParser(description="GeeksforGeeks argparse Example1",
                                 formatter_class=argparse.ArgumentDefaultsHelpFormatter)
parser.add_argument('--course', type=str, default='Python', help='Course name at GeeksforGeeks')
parser.add_argument('--duration', type=int, default=10, help='Course duration in weeks')
parser.add_argument('--level', type=str, default='Beginner', help='Course difficulty level')
args = parser.parse_args()
print(f"Course: {args.course}")
print(f"Duration: {args.duration} weeks")
print(f"Level: {args.level}")

Output:

Include default values in '--help' Using Custom Help Formatter

In this example, we are using a custom help formatter by subclassing argparse.HelpFormatter to include default values in the help message. The _get_help_string method is overridden to append the default value to each argument's help text, providing clarity on what defaults are used.

Python

import argparse
class CustomHelpFormatter(argparse.HelpFormatter):
    def _get_help_string(self, action):
        help = action.help
        if action.default is not argparse.SUPPRESS:
            help += f' (default: {action.default})'
        return help
parser = argparse.ArgumentParser(description="GeeksforGeeks argparse Example 2",
                                 formatter_class=CustomHelpFormatter)
parser.add_argument('--course', type=str, default='Python', help='Course name at GeeksforGeeks')
parser.add_argument('--duration', type=int, default=10, help='Course duration in weeks')
parser.add_argument('--level', type=str, default='Beginner', help='Course difficulty level')
args = parser.parse_args()
print(f"Course: {args.course}")
print(f"Duration: {args.duration} weeks")
print(f"Level: {args.level}")