Python CLI Patterns
Typer (Recommended)
import typer
from typing import Annotated
from pathlib import Path
from rich.console import Console
from rich.progress import track
app = typer.Typer(help="My CLI tool", no_args_is_help=True)
console = Console()
@app.command()
def process(
input_file: Annotated[Path, typer.Argument(help="Input file path")],
output_dir: Annotated[Path, typer.Option("--out", "-o", help="Output directory")] = Path("."),
verbose: Annotated[bool, typer.Option("--verbose", "-v")] = False,
workers: Annotated[int, typer.Option("--workers", "-w", min=1, max=32)] = 4,
) -> None:
"""Process input file and write results to output directory."""
if not input_file.exists():
console.print(f"[red]Error:[/red] File not found: {input_file}")
raise typer.Exit(code=1)
output_dir.mkdir(parents=True, exist_ok=True)
items = list(input_file.read_text().splitlines())
for item in track(items, description="Processing..."):
result = do_work(item)
(output_dir / f"{item}.json").write_text(result)
console.print(f"[green]Done.[/green] Wrote {len(items)} files to {output_dir}")
# Sub-commands
@app.command("validate")
def validate_cmd(path: Path) -> None:
"""Validate the configuration."""
...
if __name__ == "__main__":
app()
Rich Output Patterns
from rich.console import Console
from rich.table import Table
from rich.panel import Panel
from rich import print as rprint
console = Console()
def print_table(data: list[dict]) -> None:
table = Table(title="Results", show_header=True, header_style="bold blue")
table.add_column("Name", style="cyan")
table.add_column("Status", justify="center")
table.add_column("Duration", justify="right")
for row in data:
status_style = "green" if row["status"] == "ok" else "red"
table.add_row(
row["name"],
f"[{status_style}]{row['status']}[/{status_style}]",
f"{row['duration']:.2f}s",
)
console.print(table)
# Error output goes to stderr
console.print("[red]Error:[/red] Something went wrong", style="bold", file=console.stderr)
Configuration via Files
from pydantic_settings import BaseSettings, SettingsConfigDict
import tomllib
class CLIConfig(BaseSettings):
model_config = SettingsConfigDict(
env_prefix="MYTOOL_",
env_file=".env",
)
api_url: str = "https://api.example.com"
timeout: int = 30
def load_config(config_path: Path | None) -> CLIConfig:
if config_path and config_path.exists():
with open(config_path, "rb") as f:
toml_data = tomllib.load(f)
return CLIConfig(**toml_data.get("tool", {}).get("mytool", {}))
return CLIConfig()
Mattakushi432