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.

There are two ways to achieve this:

Adding a type parser
Expanding Click's custom types

Type Parser¶

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

Python 3.7+Python 3.7+ non-Annotated

import typer
from typing_extensions import Annotated


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)


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__":
    typer.run(main)

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)


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__":
    typer.run(main)

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.

Click Custom Type¶

If you already have a Click Custom Type, you can use it in typer.Argument() and typer.Option() with the click_type parameter.

Python 3.7+Python 3.7+ non-Annotated

import click
import typer
from typing_extensions import Annotated


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

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


class CustomClassParser(click.ParamType):
    name = "CustomClass"

    def convert(self, value, param, ctx):
        return CustomClass(value * 3)


def main(
    custom_arg: Annotated[CustomClass, typer.Argument(click_type=CustomClassParser())],
    custom_opt: Annotated[
        CustomClass, typer.Option(click_type=CustomClassParser())
    ] = "Foo",
):
    print(f"custom_arg is {custom_arg}")
    print(f"--custom-opt is {custom_opt}")


if __name__ == "__main__":
    typer.run(main)

Tip

Prefer to use the Annotated version if possible.

import click
import typer


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

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


class CustomClassParser(click.ParamType):
    name = "CustomClass"

    def convert(self, value, param, ctx):
        return CustomClass(value * 3)


def main(
    custom_arg: CustomClass = typer.Argument(click_type=CustomClassParser()),
    custom_opt: CustomClass = typer.Option("Foo", click_type=CustomClassParser()),
):
    print(f"custom_arg is {custom_arg}")
    print(f"--custom-opt is {custom_opt}")


if __name__ == "__main__":
    typer.run(main)