How to Implement argparse CLI Command in Python

Build a beginner-friendly command-line tool with argparse that accepts positional and optional arguments, flags, and prints a customizable greeting.

Easy Python 3.9+ Aug 9, 2026 Automation & scripting 15 views 0 copies

argparse cli command-line scripting automation

Python code

18 lines

Python 3.9+

import argparse


def main():
    parser = argparse.ArgumentParser(description="A simple CLI tool to greet users.")
    parser.add_argument("name", help="Your name")
    parser.add_argument("-g", "--greeting", default="Hello", help="Greeting word (default: Hello)")
    parser.add_argument("--uppercase", action="store_true", help="Print greeting in uppercase")
    args = parser.parse_args()

    message = f"{args.greeting}, {args.name}!"
    if args.uppercase:
        message = message.upper()
    print(message)


if __name__ == "__main__":
    main()

Output

stdout

$ python greet.py Alice
Hello, Alice!

$ python greet.py Alice -g Hi
Hi, Alice!

$ python greet.py Alice --uppercase
HELLO, ALICE!

$ python greet.py --help
usage: greet.py [-h] [-g GREETING] [--uppercase] name

A simple CLI tool to greet users.

positional arguments:
  name                  Your name

options:
  -h, --help            show this help message and exit
  -g GREETING, --greeting GREETING
                        Greeting word (default: Hello)
  --uppercase           Print greeting in uppercase

How it works

The argparse module is part of Python's standard library, so no third-party packages are required. add_argument defines each command-line interface element: name is a required positional argument, while -g/--greeting has a default value and --uppercase acts as a boolean flag. When you run the script, parse_args() collects the values from sys.argv and returns a namespace object whose attributes map directly to the argument names. The code then builds the message with an f-string and applies .upper() when the flag is present. Using if __name__ == "__main__" ensures the CLI logic only runs when the script is executed directly, not when imported.

Common mistakes

Forgetting that `store_true` flags don't take a value — passing one raises an error
Using `parser.parse_args` without assigning the result to a variable before accessing attributes
Putting optional arguments before the positional argument and expecting them to be parsed correctly
Forgetting the `if __name__ == "__main__"` guard, which breaks imports

Variations

Add `type=int` to an argument to parse numeric inputs automatically
Use `nargs='+'` to accept multiple positional values, e.g., multiple names

Real-world use cases

Building a deployment script that accepts environment and region as CLI arguments.
Creating a data-processing utility where users pass input and output file paths at the command line.
Writing a test-runner script that accepts a feature flag and a target module name.

How to Implement argparse CLI Command in Python

Python code

Output

How it works

Common mistakes

Variations

Real-world use cases

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Python code

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How it works

Common mistakes

Variations

Real-world use cases

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