Python CLI Patterns

Modern CLI development with Typer and Rich.

Basic Typer App

import typer

app = typer.Typer( name="myapp", help="My awesome CLI application", add_completion=True, )

@app.command() def hello( name: str = typer.Argument(..., help="Name to greet"), count: int = typer.Option(1, "--count", "-c", help="Times to greet"), loud: bool = typer.Option(False, "--loud", "-l", help="Uppercase"), ): """Say hello to someone.""" message = f"Hello, {name}!" if loud: message = message.upper() for _ in range(count): typer.echo(message)

if name == "main": app()

Command Groups

import typer

app = typer.Typer() users_app = typer.Typer(help="User management commands") app.add_typer(users_app, name="users")

@users_app.command("list") def list_users(): """List all users.""" typer.echo("Listing users...")

@users_app.command("create") def create_user(name: str, email: str): """Create a new user.""" typer.echo(f"Creating user: {name} <{email}>")

@app.command() def version(): """Show version.""" typer.echo("1.0.0")

Usage: myapp users list

myapp users create "John" "john@example.com"

myapp version

Rich Output

from rich.console import Console from rich.table import Table from rich.progress import track from rich.panel import Panel import typer

console = Console()

@app.command() def show_users(): """Display users in a table.""" table = Table(title="Users") table.add_column("ID", style="cyan") table.add_column("Name", style="green") table.add_column("Email")

users = [
    (1, "Alice", "alice@example.com"),
    (2, "Bob", "bob@example.com"),
]
for id, name, email in users:
    table.add_row(str(id), name, email)

console.print(table)

@app.command() def process(): """Process items with progress bar.""" items = list(range(100)) for item in track(items, description="Processing..."): do_something(item) console.print("[green]Done![/green]")

Error Handling

import typer from rich.console import Console

console = Console()

def error(message: str, code: int = 1): """Print error and exit.""" console.print(f"[red]Error:[/red] {message}") raise typer.Exit(code)

@app.command() def process(file: str): """Process a file.""" if not os.path.exists(file): error(f"File not found: {file}")

try:
    result = process_file(file)
    console.print(f"[green]Success:[/green] {result}")
except ValueError as e:
    error(str(e))

Quick Reference

Feature Typer Syntax

Required arg name: str

Optional arg name: str = "default"

Option typer.Option(default, "--flag", "-f")

Argument typer.Argument(..., help="...")

Boolean flag verbose: bool = False

Enum choice color: Color = Color.red

Rich Feature Usage

Table Table()

• add_column/row

Progress track(items)

Colors [red]text[/red]

Panel Panel("content", title="Title")

Additional Resources

• ./references/typer-patterns.md

• Advanced Typer patterns

• ./references/rich-output.md

• Rich tables, progress, formatting

• ./references/configuration.md

• Config files, environment variables

Assets

• ./assets/cli-template.py
• Full CLI application template

See Also

Related Skills:

• python-typing-patterns

• Type hints for CLI arguments

• python-observability-patterns

• Logging for CLI applications

Complementary Skills:

• python-env
• Package CLI for distribution