typer
Modern CLI framework built on Click using Python type hints — auto-generates CLI interfaces, help text, and shell completion from type annotations. typer features: @app.command() decorator, automatic argument/option detection from function signatures, Optional[str] for optional args, typer.Argument() and typer.Option() for metadata, typer.Typer() for multi-command apps, add_typer() for sub-apps, typer.echo() and typer.style() for colored output, typer.prompt() and typer.confirm() for interactive input, Annotated support (0.9+), automatic --help from docstrings, bash/zsh/fish shell completion, typer.Exit() and typer.Abort() for flow control, and progress bars via rich integration.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
CLI framework built on Click. Type validation prevents type confusion attacks. Secrets as CLI arguments are visible in process list and shell history — use typer.prompt(hide_input=True) for passwords: password = typer.prompt('Password', hide_input=True, confirmation_prompt=True). Environment variable fallback via envvar parameter in Option().
⚡ Reliability
Best When
Production CLIs with type safety, auto-completion, and rich help text — typer is the FastAPI creator's answer to Click with modern Python type hint ergonomics.
Avoid When
Quick prototyping (use python-fire), complex custom validation (use click), or when python-fire's zero-overhead approach is preferred.
Use Cases
- • Agent simple CLI — import typer; app = typer.Typer(); @app.command(); def main(name: str, count: int = 1, verbose: bool = False): for _ in range(count): typer.echo(f'Hello {name}'); if __name__ == '__main__': app() — typed CLI; agent creates CLI from type annotations; name is positional argument; count/verbose are options with --count/--verbose; --help auto-generated
- • Agent multi-command app — app = typer.Typer(); @app.command(); def create(name: str): ... @app.command(); def delete(name: str, force: bool = False): ... — multi-command; agent creates CLI with subcommands: python tool.py create NAME; python tool.py delete NAME --force; each @app.command() becomes a subcommand
- • Agent typed options — from typing import Optional; from typer import Option; @app.command(); def process(input: Path = Option(..., help='Input file'), output: Optional[Path] = Option(None), format: str = Option('json', '--format', '-f', help='Output format')): ... — rich options; agent uses Option() for metadata, help text, and short aliases; Path type validates file paths exist
- • Agent interactive prompts — name = typer.prompt('Enter name', default='World'); confirmed = typer.confirm('Are you sure?', abort=True) — interactive; agent prompts user for input; abort=True raises typer.Abort() if user says no; typer.prompt() with type=int validates input; useful for confirmation before destructive operations
- • Agent sub-apps — app = typer.Typer(); users_app = typer.Typer(); app.add_typer(users_app, name='users'); @users_app.command('create'); def user_create(name: str): ... — nested CLI; python tool.py users create NAME; agent builds hierarchical CLI with app groups; multiple sub-apps for logical grouping
Not For
- • Quick prototyping — typer requires more structure than python-fire; for zero-boilerplate CLI use fire
- • Complex argument validation — typer validates types but for complex custom validation use click directly
- • Non-Python-type CLIs — typer is opinionated around Python type hints; for maximum control use click
Interface
Authentication
No auth — CLI framework.
Pricing
typer is MIT licensed. Created by Sebastián Ramírez (FastAPI author). Free for all use.
Agent Metadata
Known Gotchas
- ⚠ Optional[str] vs str with default — def cmd(name: Optional[str] = None) creates optional argument; def cmd(name: str = 'default') creates required-with-default; typer distinguishes None default (optional) from string default; agent code: use Optional[str] = None for truly optional args; str = 'default' for args with default value
- ⚠ Argument vs Option semantics — positional: def cmd(name: str) — NAME is positional; named: def cmd(name: str = Option('default')) — --name NAME; agent code: use bare type annotation for positional CLI arguments; use Option() for named --flag style; Argument() for explicit positional with metadata
- ⚠ app() call required for multi-command — with @app.command() decorator, must call app() not main(); agent code: if __name__ == '__main__': app() — not main(); single-command apps can use typer.run(main) as shorthand; multi-command apps need app() always
- ⚠ Path types require exists=True for validation — from pathlib import Path; from typer import Argument; def cmd(file: Path = Argument(...)): — path is accepted but not validated; for existence check: from typer import typer; file: Path = Option(..., exists=True, file_okay=True) — or use click.Path internally; without exists=True, nonexistent paths silently pass
- ⚠ typer.echo vs print — typer.echo() is click.echo() — handles unicode correctly, flushes output, works with CliRunner in tests; print() works but CliRunner doesn't capture it in tests; agent code: use typer.echo() for all CLI output; supports err=True for stderr: typer.echo('Error', err=True)
- ⚠ Annotated syntax for complex types — typer 0.9+ supports Annotated: from typing import Annotated; def cmd(name: Annotated[str, typer.Argument(help='Name')]): ... — clean type annotations; older syntax: def cmd(name: str = typer.Argument(..., help='Name')); agent code for new projects: use Annotated for cleaner type annotations; mixing old and new syntax in same app is valid
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Scores are editorial opinions as of 2026-03-06.