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**:

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

## Example ### The absolute minimum * Create a file `main.py` with: ```Python 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:

```console // 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: ```Python import typer def main(name: str): print(f"Hello {name}") if __name__ == "__main__": typer.run(main) ``` Now you could run it with Python directly:

```console // 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. ```Python hl_lines="3 6 11 20" 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:

```console $ 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:

```console $ 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:

```console $ 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:

```console // 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](https://typer.tiangolo.com/tutorial/commands/one-or-multiple/) 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`: ```Python total: int ``` or for a `bool` flag: ```Python 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 giants. It has three required dependencies: * Click: a popular tool for building CLIs in Python. Typer is based on it. * rich: to show nicely formatted errors automatically. * shellingham: to automatically detect the current shell when installing completion. ### `typer-slim` There used to be a slimmed-down version of Typer called `typer-slim`, which didn't include the dependencies `rich` and `shellingham`, nor the `typer` command. However, since version 0.22.0, we have stopped supporting this, and `typer-slim` now simply installs (all of) Typer. If you want to disable Rich globally, you can set an environmental variable `TYPER_USE_RICH` to `False` or `0`. ## License This project is licensed under the terms of the MIT license.

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