Python Argparse Module

The argparse module helps you build command-line interfaces with positional arguments, options, flags, and help messages.

The module was added in Python 3.2. If you are using Python 3.14, ArgumentParser also supports the suggest_on_error and color parameters.

import argparse

Use argparse when you want a Python file to behave like a small terminal program:

python greet.py Ada --count 2

The module reads the text after the script name, validates it, and gives you a Python object with the parsed values.

Creating a parser

ArgumentParser stores the arguments your program accepts.

import argparse

parser = argparse.ArgumentParser(
    prog='greet',
    description='Greet a user from the command line',
)

parser.print_help()

usage: greet [-h]

Greet a user from the command line

options:
  -h, --help  show this help message and exit

Positional arguments

Positional arguments are required by default.

import argparse

parser = argparse.ArgumentParser()
parser.add_argument('name')

args = parser.parse_args(['Ada'])
print(args.name)

Ada

Optional arguments and flags

Optional arguments usually start with - or --.

import argparse

parser = argparse.ArgumentParser()
parser.add_argument('--count', type=int, default=1)
parser.add_argument('-v', '--verbose', action='store_true')

args = parser.parse_args(['--count', '3', '--verbose'])
print(args.count)
print(args.verbose)

3
True

Choices and type conversion

You can validate values as they are parsed.

import argparse

parser = argparse.ArgumentParser()
parser.add_argument('--mode', choices=['dev', 'prod'])
parser.add_argument('--port', type=int, default=8000)

args = parser.parse_args(['--mode', 'dev', '--port', '9000'])
print(args.mode)
print(args.port)

dev
9000

Subcommands

Subcommands are useful for tools like git commit or docker run.

import argparse

parser = argparse.ArgumentParser()
subparsers = parser.add_subparsers(dest='command', required=True)

build_parser = subparsers.add_parser('build')
build_parser.add_argument('--release', action='store_true')

args = parser.parse_args(['build', '--release'])
print(args.command)
print(args.release)

build
True

A small complete example

This example accepts a name and repeats the greeting.

import argparse

parser = argparse.ArgumentParser()
parser.add_argument('name')
parser.add_argument('--count', type=int, default=1)

args = parser.parse_args(['Ada', '--count', '2'])

for _ in range(args.count):
    print(f'Hello {args.name}!')

Hello Ada!
Hello Ada!