Skip to content

Tutorial - User Guide - Intro

Python types

If you need a refresher about how to use Python type hints, check the first part of FastAPI's Python types intro.

You can also check the mypy cheat sheet.

In short (very short), you can declare a function with parameters like:

from typing import Optional

def type_example(name: str, formal: bool = False, intro: Optional[str] = None):
    pass

And your editor (and Typer) will know that:

  • name is of type str and is a required parameter.
  • formal is a bool and is by default False.
  • intro is an optional str, by default is None.

These type hints are what give you autocomplete in your editor and several other features.

Typer is based on these type hints.

Intro

This tutorial shows you how to use Typer with all its features, step by step.

Each section gradually builds on the previous ones, but it's structured to separate topics, so that you can go directly to any specific one to solve your specific CLI needs.

It is also built to work as a future reference.

So you can come back and see exactly what you need.

Run the code

All the code blocks can be copied and used directly (they are tested Python files).

To run any of the examples, copy the code to a file main.py, and run it:

$ python main.py

✨ The magic happens here ✨

It is HIGHLY encouraged that you write or copy the code, edit it and run it locally.

Using it in your editor is what really shows you the benefits of Typer, seeing how little code you have to write, all the type checks, autocompletion, etc.

And running the examples is what will really help you understand what is going on.

You can learn a lot more by running some examples and playing around with them than by reading all the docs here.

Install Typer

The first step is to install Typer:

$ pip install typer
---> 100%
Successfully installed typer click shellingham rich

By default, typer comes with rich and shellingham.

Note

If you are an advanced user and want to opt out of these default extra dependencies, you can instead install typer-slim.

pip install typer

...includes the same optional dependencies as:

pip install "typer-slim[standard]"