Typer, build great CLIs. Easy to code. Based on Python type hints.

Documentation: https://typer.tiangolo.com

Source Code: https://github.com/fastapi/typer

Typer is a library for building CLI applications that users will love using and developers will love creating. Based on Python type hints.

It's also a command line tool to run scripts, automatically converting them to CLI applications.

The key features are:

- Intuitive to write: Great editor support. Completion everywhere. Less time debugging. Designed to be easy to use and learn. Less time reading docs.
- Easy to use: It's easy to use for the final users. Automatic help, and automatic completion for all shells.
- Short: Minimize code duplication. Multiple features from each parameter declaration. Fewer bugs.
- Start simple: The simplest example adds only 2 lines of code to your app: 1 import, 1 function call.
- Grow large: Grow in complexity as much as you want, create arbitrarily complex trees of commands and groups of subcommands, with options and arguments.
- Run scripts: Typer includes a `typer` command/program that you can use to run scripts, automatically converting them to CLIs, even if they don't use Typer internally.

## FastAPI of CLIs

Typer is FastAPI's little sibling, it's the FastAPI of CLIs.

## Installation

Create and activate a virtual environment and then install Typer:

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

## Example

### The absolute minimum

- Create a file `main.py` with:

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

This script doesn't even use Typer internally. But you can use the `typer` command to run it as a CLI application.

### Run it

Run your application with the `typer` command:

    // Run your application
    $ typer main.py run

    // You get a nice error, you are missing NAME
    Usage: typer [PATH_OR_MODULE] run [OPTIONS] NAME
    Try 'typer [PATH_OR_MODULE] run --help' for help.
    ╭─ Error ───────────────────────────────────────────╮
    │ Missing argument 'NAME'.                          │
    ╰───────────────────────────────────────────────────╯

    // You get a --help for free
    $ typer main.py run --help

    Usage: typer [PATH_OR_MODULE] run [OPTIONS] NAME

    Run the provided Typer app.

    ╭─ Arguments ───────────────────────────────────────╮
    │ *    name      TEXT  [default: None] [required]   |
    ╰───────────────────────────────────────────────────╯
    ╭─ Options ─────────────────────────────────────────╮
    │ --help          Show this message and exit.       │
    ╰───────────────────────────────────────────────────╯

    // Now pass the NAME argument
    $ typer main.py run Camila

    Hello Camila

    // It works! 🎉

This is the simplest use case, not even using Typer internally, but it can already be quite useful for simple scripts.

Note: auto-completion works when you create a Python package and run it with `--install-completion` or when you use the `typer` command.

## Use Typer in your code

Now let's start using Typer in your own code, update `main.py` with:

    import typer

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

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

Now you could run it with Python directly:

    // Run your application
    $ python main.py

    // You get a nice error, you are missing NAME
    Usage: main.py [OPTIONS] NAME
    Try 'main.py --help' for help.
    ╭─ Error ───────────────────────────────────────────╮
    │ Missing argument 'NAME'.                          │
    ╰───────────────────────────────────────────────────╯

    // You get a --help for free
    $ python main.py --help

    Usage: main.py [OPTIONS] NAME

    ╭─ Arguments ───────────────────────────────────────╮
    │ *    name      TEXT  [default: None] [required]   |
    ╰───────────────────────────────────────────────────╯
    ╭─ Options ─────────────────────────────────────────╮
    │ --help          Show this message and exit.       │
    ╰───────────────────────────────────────────────────╯

    // Now pass the NAME argument
    $ python main.py Camila

    Hello Camila

    // It works! 🎉

Note: you can also call this same script with the `typer` command, but you don't need to.

## Example upgrade

This was the simplest example possible.

Now let's see one a bit more complex.

### An example with two subcommands

Modify the file `main.py`.

Create a `typer.Typer()` app, and create two subcommands with their parameters.

    import typer

    app = typer.Typer()

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

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

    if __name__ == "__main__":
        app()

And that will:

- Explicitly create a `typer.Typer` app.
  - The previous `typer.run` actually creates one implicitly for you.
- Add two subcommands with `@app.command()`.
- Execute the `app()` itself, as if it was a function (instead of `typer.run`).

### Run the upgraded example

Check the new help:

    $ python main.py --help

     Usage: main.py [OPTIONS] COMMAND [ARGS]...

    ╭─ Options ─────────────────────────────────────────╮
    │ --install-completion          Install completion  │
    │                               for the current     │
    │                               shell.              │
    │ --show-completion             Show completion for │
    │                               the current shell,  │
    │                               to copy it or       │
    │                               customize the       │
    │                               installation.       │
    │ --help                        Show this message   │
    │                               and exit.           │
    ╰───────────────────────────────────────────────────╯
    ╭─ Commands ────────────────────────────────────────╮
    │ goodbye                                           │
    │ hello                                             │
    ╰───────────────────────────────────────────────────╯

    // When you create a package you get ✨ auto-completion ✨ for free, installed with --install-completion

    // You have 2 subcommands (the 2 functions): goodbye and hello

Now check the help for the `hello` command:

    $ python main.py hello --help

     Usage: main.py hello [OPTIONS] NAME

    ╭─ Arguments ───────────────────────────────────────╮
    │ *    name      TEXT  [default: None] [required]   │
    ╰───────────────────────────────────────────────────╯
    ╭─ Options ─────────────────────────────────────────╮
    │ --help          Show this message and exit.       │
    ╰───────────────────────────────────────────────────╯

And now check the help for the `goodbye` command:

    $ python main.py goodbye --help

     Usage: main.py goodbye [OPTIONS] NAME

    ╭─ Arguments ───────────────────────────────────────╮
    │ *    name      TEXT  [default: None] [required]   │
    ╰───────────────────────────────────────────────────╯
    ╭─ Options ─────────────────────────────────────────╮
    │ --formal    --no-formal      [default: no-formal] │
    │ --help                       Show this message    │
    │                              and exit.            │
    ╰───────────────────────────────────────────────────╯

    // Automatic --formal and --no-formal for the bool option 🎉

Now you can try out the new command line application:

    // Use it with the hello command

    $ python main.py hello Camila

    Hello Camila

    // And with the goodbye command

    $ python main.py goodbye Camila

    Bye Camila!

    // And with --formal

    $ python main.py goodbye --formal Camila

    Goodbye Ms. Camila. Have a good day.

Note: If your app only has one command, by default the command name is omitted in usage: `python main.py Camila`. However, when there are multiple commands, you must explicitly include the command name: `python main.py hello Camila`. See One or Multiple Commands for more details.

### Recap

In summary, you declare once the types of parameters (CLI arguments and CLI options) as function parameters.

You do that with standard modern Python types.

You don't have to learn a new syntax, the methods or classes of a specific library, etc.

Just standard Python.

For example, for an `int`:

    total: int

or for a `bool` flag:

    force: bool

And similarly for files, paths, enums (choices), etc. And there are tools to create groups of subcommands, add metadata, extra validation, etc.

You get: great editor support, including completion and type checks everywhere.

Your users get: automatic `--help`, auto-completion in their terminal (Bash, Zsh, Fish, PowerShell) when they install your package or when using the `typer` command.

For a more complete example including more features, see the Tutorial - User Guide.

## Dependencies

Typer stands on the shoulders of a giant. Its only internal required dependency is Click.

By default it also comes with extra standard dependencies:

- `rich`: to show nicely formatted errors automatically.
- `shellingham`: to automatically detect the current shell when installing completion.
  - With `shellingham` you can just use `--install-completion`.
  - Without `shellingham`, you have to pass the name of the shell to install completion for, e.g. `--install-completion bash`.

### `typer-slim`

If you don't want the extra standard optional dependencies, install `typer-slim` instead.

When you install with:

    pip install typer

...it includes the same code and dependencies as:

    pip install "typer-slim[standard]"

The `standard` extra dependencies are `rich` and `shellingham`.

Note: The `typer` command is only included in the `typer` package.

## License

This project is licensed under the terms of the MIT license.

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