Typer Skip to content Typer Search fastapi/typer Typer Features Learn Reference Resources About Release Notes Typer fastapi/typer Typer Typer On this page FastAPI of CLIs Installation Example The absolute minimum Run it Use Typer in your code Example upgrade An example with two subcommands Run the upgraded example Recap Dependencies Click code typer-slim License Features Learn Install Typer First Steps Typer App Printing and Colors Terminating CLI Arguments Optional CLI Arguments CLI Arguments with Default CLI Arguments with Help CLI Arguments with Environment Variables Other uses CLI Options CLI Options with Help Required CLI Options CLI Option Prompt Password CLI Option and Confirmation Prompt CLI Option Name CLI Option Callback and Context Version CLI Option, is_eager Commands Command CLI Arguments Command CLI Options Command Help Custom Command Name Typer Callback One or Multiple Commands Using the Context CLI Option autocompletion CLI Parameter Types Number Boolean CLI Options UUID DateTime Enum - Choices Path File Custom Types SubCommands - Command Groups Add Typer SubCommands in a Single File Nested SubCommands Sub-Typer Callback Override SubCommand Name and Help Multiple Values Multiple CLI Options CLI Options with Multiple Values CLI Arguments with Multiple Values Ask with Prompt Progress Bar CLI Application Directory Launching Applications Testing Building a Package Exceptions and Errors One File Per Command typer command Vendored Click Reference Typer class run and launch Parameters File objects Context Resources Help Development - Contributing About Alternatives, Inspiration and Comparisons Repository Management Release Notes On this page FastAPI of CLIs Installation Example The absolute minimum Run it Use Typer in your code Example upgrade An example with two subcommands Run the upgraded example Recap Dependencies Click code typer-slim License ¶ 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¶ First, install uv, and then add Typer to your project: $ uv add typer ---> 100% This installs both the Typer library and the typer command in the project's virtual environment. To use typer directly with shell completion, activate the project environment and install completion. If you prefer to use pip, install typer inside a virtual environment. See the installation guide for the alternative steps. 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 <str> [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 $ uv run 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 $ uv run python main.py --help Usage: main.py [OPTIONS] {name} ╭─ Arguments ───────────────────────────────────────╮ │ * name <str> [required] │ ╰───────────────────────────────────────────────────╯ ╭─ Options ─────────────────────────────────────────╮ │ --help Show this message and exit. │ ╰───────────────────────────────────────────────────╯ // Now pass the 'name' argument $ uv run 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: $ uv run 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 ────────────────────────────────────────╮ │ hello │ │ goodbye │ ╰───────────────────────────────────────────────────╯ // When you create a package you get ✨ auto-completion ✨ for free, installed with --install-completion // You have 2 subcommands (the 2 functions): hello and goodbye Now check the help for the hello command: $ uv run python main.py hello --help Usage: main.py hello [OPTIONS] {name} ╭─ Arguments ───────────────────────────────────────╮ │ * name <str> [required] │ ╰───────────────────────────────────────────────────╯ ╭─ Options ─────────────────────────────────────────╮ │ --help Show this message and exit. │ ╰───────────────────────────────────────────────────╯ And now check the help for the goodbye command: $ uv run python main.py goodbye --help Usage: main.py goodbye [OPTIONS] {name} ╭─ Arguments ───────────────────────────────────────╮ │ * name <str> [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 $ uv run python main.py hello Camila Hello Camila // And with the goodbye command $ uv run python main.py goodbye Camila Bye Camila! // And with --formal $ uv run 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…