Typer

Practical examples

Single-command script

import typer

def main(name: str):
    print(f"Hello {name}")

if __name__ == "__main__":
    typer.run(main)

Multi-command app

from typing import Annotated

import typer

app = typer.Typer(no_args_is_help=True)

@app.command()
def hello(name: str):
    print(f"Hello {name}")

@app.command()
def goodbye(
    name: str,
    formal: Annotated[bool, typer.Option(help="Use a formal goodbye")] = False,
):
    if formal:
        print(f"Goodbye Ms. {name}. Have a good day.")
    else:
        print(f"Bye {name}!")

if __name__ == "__main__":
    app()

Testing a Typer app

from typer.testing import CliRunner

from .main import app

runner = CliRunner()

def test_hello():
    result = runner.invoke(app, ["hello", "Camila"])
    assert result.exit_code == 0
    assert "Hello Camila" in result.output

Testing prompt input

from typing import Annotated

import typer
from typer.testing import CliRunner

app = typer.Typer()

@app.command()
def subscribe(
    email: Annotated[str, typer.Option(prompt="Email address")],
):
    print(email)

runner = CliRunner()

def test_prompt():
    result = runner.invoke(app, ["subscribe"], input="[email protected]\n")
    assert result.exit_code == 0
    assert "[email protected]" in result.output

Evaluation guidance

When refining this skill or reviewing advice produced with it:

• use at least one single-command prompt and one multi-command prompt
• verify that the guidance respects Typer's one-command versus many-command behavior
• prefer examples that a reader can run or test immediately
• treat completion claims that ignore installed entry points or the typer command as failures
• treat tests that skip CliRunner for ordinary CLI behavior as a warning sign

Sources

• Typer:
  • Home
  • Tutorial: Commands
  • Tutorial: Testing