How create an option with an optional argument (e.g. a flag with an optional value)

[taranlu-houzz]

First Check

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• I already checked if it is not related to Typer but to Click.

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Example Code

from pprint import pprint as pp
from typing import Optional
import typer


APP = typer.Typer(
    rich_markup_mode="markdown",
    pretty_exceptions_show_locals=False,
)


@APP.command()
def test(
    opt_1: Optional[float] = typer.Option(
        None,
        "--opt-1",
        is_flag=False,
        flag_value=3.14,
        help="blah blah",
    ),
) -> None:
    pp(locals())


if __name__ == "__main__":
    APP()

Description

In click, it is possible to create an option with an optional value: https://click.palletsprojects.com/en/8.1.x/options/#optional-value

I'm wondering if it is possible to do this in typer?

For the example given above, I would expect the following:

• No --opt-1 flag passed: None
• --opt-1 flag is passed with no value: 3.14 (default value)
• --opt-1 flag is passed with a value (99): 99 (value that was passed)

Operating System

macOS

Operating System Details

No response

Typer Version

0.9.0

Python Version

3.10.10

Additional Context

No response

[e-sr]

some hints? how to do this?
I tried like in clik docs:

@app.command()
def test_flag(flag: Optional[str] = typer.Option(None, is_flag=False, flag_value='default')):
    if flag is not None:
        print(f"{flag=}")
    else:
        print("flag unset")

calling
app test-flag is ok
app test-flag --flag is ok
app test-flag --flag=nodefault raise an exception

Option '--flag' does not take a value.                                                                                           │

what is the purpose of parameter is_flag