Modern Python CLI

Note

This tutorial is designed for data scientists who usually run scripts with:

python script.py

We will show you how to transform such scripts into a real Command-Line Interface (CLI). First, we start with a very simple library called click. Then, we move on to a modern, professional stack with Typer, Rich, Questionary, and Pyfiglet.

source:

Part 1: A First CLI with click

Initiating a uv project

uv init --package tuto_cli

Installing click

Install the library with:

uv add click

Creating the File

Create a file called src/tuto_cli/cli_basic.py in your project folder:

import click

 @click.group()
 def main():
     pass

 @main.command()
 @click.argument("price", type=float)
 @click.argument("quantity", type=int)
 @click.option("--taxes", default=0.0, type=float, help="Tax percentage")
 def total(price, quantity, taxes):
     """Compute the total cost with optional taxes"""
     subtotal = price * quantity
     total_value = subtotal * (1 + taxes / 100)
     print(f"💰 Price: {price} € x {quantity} = {subtotal:.2f} €")
     if taxes > 0:
         print(f"➕ Taxes: {taxes}% → Total = {total_value:.2f} €")

 if __name__ == "__main__":
     main()

Running the CLI

Execute the script with:

uv run src/tuto_cli/cli_basic.py total 10 3 --taxes 20

Output:

💰 Price: 10.0 € x 3 = 30.00 €
➕ Taxes: 20.0% → Total = 36.00 €

Limitations of click

• Minimal features: no colors, no tables, no progress bars.

• No interactivity: you cannot ask the user for confirmation or choices.

• Low maintenance: cli is not widely used or updated.

• Poor documentation compared to modern frameworks.

This is why we now move on to a modern stack.

Part 2: A Modern CLI with Typer

Installing Dependencies

Add the following libraries:

uv add typer[all] rich questionary pyfiglet

Writing the CLI

Open src/tuto_cli/cli.py :

import typer
import pyfiglet
import questionary
from rich.console import Console

app = typer.Typer()
console = Console()

@app.command()
def total(
    price: float = typer.Option(..., "--price", "-p", help="Unit price in euros"),
    quantity: int = typer.Option(..., "--quantity", "-q", help="Number of items"),
    taxes: float = typer.Option(0.0, "--taxes", "-t", help="Tax rate (%)"),
):
    """
    Compute the total cost of items, optionally with taxes.
    """

    # Pyfiglet banner
    banner = pyfiglet.figlet_format("Total CLI")
    console.print(f"[bold cyan]{banner}[/bold cyan]")

    # Confirmation with Questionary
    confirm = questionary.confirm(
        f"Do you want to calculate {quantity} item(s) at {price}€ with {taxes}% taxes?"
    ).ask()

    if confirm:
        subtotal = price * quantity
        total_value = subtotal * (1 + taxes / 100)
        console.print(f"💰 [green]Subtotal[/green]: {subtotal:.2f} €")
        if taxes > 0:
            console.print(
                f"➕ [blue]Taxes ({taxes}%)[/blue] → "
                f"[bold yellow]{total_value:.2f} €[/bold yellow]"
            )
        else:
            console.print(f"✅ [bold yellow]Total[/bold yellow]: {total_value:.2f} €")
    else:
        console.print("[red]Operation cancelled.[/red]")

if __name__ == "__main__":
    app()

Running the CLI

Run with:

uv run src/tuto_cli/cli.py --price 10 --quantity 3 --taxes 20

Example Output:

 _______          _        _____ _      _____
|__   __|        | |      / ____| |    |_   _|
   | | ___   ___ | | __  | |    | |      | |
   | |/ _ \ / _ \| |/ /  | |    | |      | |
   | | (_) | (_) |   <   | |____| |____ _| |_
   |_|\___/ \___/|_|\_\   \_____|______|_____|

 ? Do you want to calculate 3 item(s) at 10.0€ with 20.0% taxes? Yes
 💰 Subtotal: 30.00 €
 ➕ Taxes (20.0%) → 36.00 €

Exploring Help

Typer auto-generates documentation:

uv run src/tuto_cli/cli.py --help

Output:

Usage: cli.py [OPTIONS]

Compute the total cost of items, optionally with taxes.

╭─ Options ────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ *  --price               -p      FLOAT    Unit price in euros [required]                                             │
│ *  --quantity            -q      INTEGER  Number of items [required]                                                 │
│    --taxes               -t      FLOAT    Tax rate (%) [default: 0.0]                                                │
│    --install-completion                   Install completion for the current shell.                                  │
│    --show-completion                      Show completion for the current shell, to copy it or customize the         │
│                                           installation.                                                              │
│    --help                                 Show this message and exit.                                                │
╰──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯

Benchmark: click vs Typer

Here is a comparison between the two approaches:

Feature	click (basic)	Typer + Rich stack
Maintenance	Low, rarely updated	Active, large community
Arguments & options	Supported	Supported + full help
Colors & formatting	No	Yes (via Rich)
Interactivity	No	Yes (via Questionary)
ASCII art banners	No	Yes (via Pyfiglet)
Help & documentation	Minimal	Auto-generated, detailed
Use cases	Quick demos	Professional-grade tools

Conclusion

• click is fine for a very quick experiment, but limited.

• Typer + Rich + Questionary + Pyfiglet turns your script into a professional tool.

• For data scientists, this means you can share cleaner, friendlier tools with colleagues, automate pipelines, and create impressive demos.

Next Steps

• Add more commands (e.g. discount or convert).

• Connect the CLI to your data pipeline or machine learning scripts.

• Share it as a Python package with your team.

With these steps, you just learned how to level up your Python scripts into real, user-friendly CLIs. 🎉