Context

Every app has a special internal object that keeps track of state relevant to the script's execution. For some advanced use-cases, you may want to access it directly. This can be done by declaring a function parameter of type typer.Context.

Similarly, you can also declare a function parameter with type typer.CallbackParam in case a callback could be used by several CLI parameters, and you need to figure out which one it was.

from typing import Annotated

import typer

app = typer.Typer()


def name_callback(ctx: typer.Context, param: typer.CallbackParam, value: str):
    if ctx.resilient_parsing:
        return
    print(f"Validating param: {param.name}")
    if value != "Rick":
        raise typer.BadParameter("Only Rick is allowed")
    return value


@app.command()
def main(name: Annotated[str | None, typer.Option(callback=name_callback)] = None):
    print(f"Hello {name}")


if __name__ == "__main__":
    app()

typer.Context

Bases: Context

The Context has some additional data about the current execution of your program. When declaring it in a callback function, you can access this additional information.

typer.CallbackParam

Bases: Parameter

In a callback function, you can declare a function parameter with type CallbackParam to access the specific Click Parameter object.