Typer, build great CLIs. Easy to code. Based on Python type hints.
---
**Documentation**: https://typer.tiangolo.com
**Source Code**: https://github.com/tiangolo/typer
---
Typer is a library for building CLI applications that users will **love using** and developers will **love creating**. Based on Python 3.6+ type hints.
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.
## FastAPI of CLIs
**Typer** is FastAPI's little sibling.
And it's intended to be the FastAPI of CLIs.
## Requirements
Python 3.6+
**Typer** stands on the shoulders of a giant. Its only internal dependency is Click.
## Installation
```console
$ pip install "typer[all]"
---> 100%
Successfully installed typer
```
**Note**: that will include Rich. Rich is the recommended library to *display* information on the terminal, it is optional, but when installed, it's deeply integrated into **Typer** to display beautiful output.
## Example
### The absolute minimum
* Create a file `main.py` with:
```Python
import typer
def main(name: str):
print(f"Hello {name}")
if __name__ == "__main__":
typer.run(main)
```
### Run it
Run your application:
```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 ─────────────────────────────────────────╮
│ --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. │
╰───────────────────────────────────────────────────╯
// When you create a package you get ✨ auto-completion ✨ for free, installed with --install-completion
// Now pass the NAME argument
$ python main.py Camila
Hello Camila
// It works! 🎉
```
**Note**: auto-completion works when you create a Python package and run it with `--install-completion` or when you use Typer CLI.
## 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 │
╰───────────────────────────────────────────────────╯
// 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.
```
### 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 3.6+**.
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 Typer CLI.
For a more complete example including more features, see the Tutorial - User Guide.
## Optional Dependencies
Typer uses Click internally. That's the only dependency.
But you can also install extras:
* rich: and Typer will show nicely formatted errors automatically.
* shellingham: and Typer will 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`.
You can install `typer` with `rich` and `shellingham` with `pip install typer[all]`.
## License
This project is licensed under the terms of the MIT license.