Typer CLI

Typer CLI runs Python scripts with arguments, help and type validation even when the script does not import Typer itself.

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  • MIT
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Why this level

  • The command executes Python scripts and imports with current-process permissions.
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fastapi/typer

Install

In your terminal, with SkillFoxx CLI

npx skillfoxx add cli/typer-cli

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How we review

Extended accessThe tool runs code or makes network calls and only reads external data.

  • The command executes Python scripts and imports with current-process permissions.

This is third-party code. Review the repository files before installing.

What it does

Typer reads a Python function signature and builds a command-line interface: parameter names become arguments and annotations define expected types. If a required argument is missing, the error names it and shows how to open help. The function body can stay unchanged. The CLI suits an existing utility script. For an application with several operations, the author creates `typer.Typer()` and marks functions with `@app.command()`. Help then lists separate subcommands with their own arguments, which can be invoked through Python.

Who it is for. Authors of small Python scripts needing clear arguments and help without separate CLI boilerplate.

Good fit when

  • A colleague runs a utility script but cannot remember its arguments.
  • A finished Python function needs a command-line interface.
  • Numbers and paths arrive from a shell where input-type mistakes are common.
  • Several utility operations have grown into an application with subcommands.

Not a fit when

  • The selected Python script may not be executed.
  • Type hints must prove business-logic correctness.
  • You need a finished task tool without supplying a script.

Example request

Show Typer CLI help for my reviewed main.py and explain arguments without executing production work.

Limitations

The first installation adds Typer through uv to a project; its executable lives in that project’s `.venv`, not a global environment. Direct `typer` calls and shell completion require that environment to be active in the current terminal. The interface follows function signatures and annotations: input validation does not prove application logic correct. The script and its imports run with process permissions, so even requesting help should be limited to trusted code.

How to disable. Stop the script and remove the project dependency if needed. Its command belongs to that environment.

FAQ

How do I pass an argument to an ordinary function?

The README’s `main(name: str)` function in `main.py` prints a greeting. `typer main.py run Camila` passes the name and prints `Hello Camila`.

How do I inspect example arguments?

Use `typer main.py run --help` with a reviewed file.

The command is missing after `uv add typer`?

It is installed in the project’s `.venv`. On Linux or macOS, run `source .venv/bin/activate` from the project directory, then retry `typer`. Other shells have their own activation command in the official installation guide.

Where do argument types come from?

From function annotations: for example, a string parameter becomes a string argument. Help describes expected input.

How do I invoke the same example through Python?

Add `import typer` and call `typer.run(main)` under `if __name__ == "__main__"`. Then `uv run python main.py Camila` prints the same greeting.

Discussion

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README in short

Subcommands have their own help: in the expanded example, `uv run python main.py hello --help` displays arguments for `hello` alone.

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