Command-Line Apps (argparse)

Build professional command-line tools with Python's argparse module.

Basic argparse Usage

argparse is the industry-standard library for building command-line interfaces (CLIs) in Python. It handles help messages, error checking, and argument parsing automatically.

key Concepts

1. Parser: The container for your argument specifications.
2. Arguments: The inputs your program expects.
3. Parsing: converting text input into Python objects.

Example

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("name", help="Your name")
args = parser.parse_args()
print(f"Hello {args.name}")

Optional Arguments

Arguments can be positional (required, determined by order) or optional (flags starting with - or --).

Optional arguments are typically used for configuration or flags (like --verbose).

Example

parser.add_argument("-v", "--verbose", action="store_true")
# Usage: python script.py -v

Subcommands

Complex applications (like git or docker) use subcommands to group functionality (e.g., git push, git pull). argparse supports this via add_subparsers.

Example

subparsers = parser.add_subparsers(dest="command")

# 'add' command
add_parser = subparsers.add_parser("add")
add_parser.add_argument("filename")

Complete CLI Application

Quiz

Key Takeaways

✅ argparse for professional CLI apps.
✅ Positional arguments are required.
✅ Optional arguments start with - or --.
✅ Subcommands create git-like interfaces.
✅ Help messages auto-generated.

Module 6 Complete! 🎉

You've mastered automation and CLI tools! Next up: Web Development with Python.

Keep coding! 🚀