CLI Tools Competent¶

🌐 Web & APIs Track · Level 2

⏱️ ~3 days 📚 Prerequisite: Functions

When you'd use this

Build command-line interfaces with argparse, click and typer.

Build command-line tools — scripts with flags, subcommands, and help text — using argparse, click, or typer instead of parsing sys.argv by hand.

argparse (built-in)¶

The standard-library parser — no dependencies. Use for scripts where you don't want to add a package.

import argparse

parser = argparse.ArgumentParser(description="Greet someone")
parser.add_argument("name", help="Name to greet")
parser.add_argument("-n", "--times", type=int, default=1, help="Times to greet")

args = parser.parse_args()
for _ in range(args.times):
    print(f"Hello, {args.name}!")

python greet.py Alice --times 3

click (third-party, declarative)¶

Build CLIs with decorators and automatic help — use for richer tools with subcommands and options.

import click

@click.command()
@click.argument("name")
@click.option("--times", "-n", default=1, help="Times to greet")
def greet(name, times):
    """Greet someone NAME times."""
    for _ in range(times):
        click.echo(f"Hello, {name}!")

if __name__ == "__main__":
    greet()

typer (modern, type-hint based)¶

Define commands with plain type-hinted functions — the least-boilerplate option, built on click.

import typer

app = typer.Typer()

@app.command()
def greet(name: str, times: int = 1):
    """Greet someone."""
    for _ in range(times):
        typer.echo(f"Hello, {name}!")

if __name__ == "__main__":
    app()

When to use what¶

Pick argparse for zero-dependency scripts, click/typer for larger multi-command tools.

Tool	Best for
`argparse`	Standard library, no deps, simple scripts
`click`	Multi-command CLIs, complex options
`typer`	Modern apps, type hints, auto-completion

Practice exercises¶

Build a file search CLI: finder --ext .py --path ./src
Create a multi-command CLI with add, remove, list subcommands.
Add auto-completion and colored output with typer/rich.

💬 Discussion

Have a question about this topic? Found an error? Share your thoughts below.