Custom Types¶

You can easily use your own custom types in your Typer applications.

The way to do it is by providing a way to parse input into your own types.

Type Parser¶

typer.Argument and typer.Option can create custom parameter types with a parser callable.

Python 3.9+

from typing import Annotated

import typer


class CustomClass:
    def __init__(self, value: str):
        self.value = value

    def __str__(self):
        return f"<CustomClass: value={self.value}>"


def parse_custom_class(value: str):
    return CustomClass(value * 2)


app = typer.Typer()


@app.command()
def main(
    custom_arg: Annotated[CustomClass, typer.Argument(parser=parse_custom_class)],
    custom_opt: Annotated[CustomClass, typer.Option(parser=parse_custom_class)] = "Foo",
):
    print(f"custom_arg is {custom_arg}")
    print(f"--custom-opt is {custom_opt}")


if __name__ == "__main__":
    app()

🤓 Other versions and variants

Python 3.9+ - non-Annotated

Tip

Prefer to use the Annotated version if possible.

import typer


class CustomClass:
    def __init__(self, value: str):
        self.value = value

    def __str__(self):
        return f"<CustomClass: value={self.value}>"


def parse_custom_class(value: str):
    return CustomClass(value * 2)


app = typer.Typer()


@app.command()
def main(
    custom_arg: CustomClass = typer.Argument(parser=parse_custom_class),
    custom_opt: CustomClass = typer.Option("Foo", parser=parse_custom_class),
):
    print(f"custom_arg is {custom_arg}")
    print(f"--custom-opt is {custom_opt}")


if __name__ == "__main__":
    app()

The function (or callable) that you pass to the parameter parser will receive the input value as a string and should return the parsed value with your own custom type.