What's the right way to programmatically set the selected RadioButton within a RadioSet?

[lauralindzey]

I have a RadioSet with a bunch of RadioButtons, e.g.:

RadioSet(
    RadioButton("task 1a", classes="task1", value=True),
    RadioButton("task 1b", classes="task1", value=False),
    RadioButton("task 2a", classes="task2", value=False),
    RadioButton("task 2b", classes="task2", value=False),
    id = "target_radio_set"
)

Only a subset of them should be visible at any time, depending on the state of the rest of the program. I've figured out two ways to do that:

1. directly set .display on each RadioButton, directly update this when the program state changes.

buttons = self.query("#target_radio_set>RadioButton.task1")
for obj in buttons:
        obj.display = True

2. assign RadioButtons to classes, and have another class that updates when the program state changes. Use tcss to manage display based on these two classes. e.g.:

.task2_active #target_radio_set>RadioButton{
    display: none;
    &.task2 {
        display: block;
    }
}

However, once I have the proper radio buttons displaying, I want to either totally clear the RadioSet's state so that no buttons are active, or to default to the first displayed button being set to active. Is it possible to do either of these programmatically? (The important bit here is that if I query the RadioSet's state via pressed_button, it should never return a RadioButton that isn't currently displayed.)

I've tried setting button.value=True on an appropriate RadioButton itself, but that totally borks the RadioSet's functionality -- that button never turns off, even if I click another one in the set. I get similar behavior if I try button.toggle(). The only time setting value directly seems to work is in the actual constructor, when I'm creating the RadioSet.

I also tried button.emit(...) based on this discussion, but get the error "AttributeError: 'RadioButton' object has no attribute 'emit'"

[davep]

I feel you're trying to do a little more with RadioSet than it was intended to do. If I wanted a RadioSet whose content depended on the state of some other part of my application, I'd probably take an approach where I remove the existing one and mount fresh one in its place with the desired buttons.

As an illustration:

from textual import on
from textual.app import App, ComposeResult
from textual.containers import Vertical
from textual.widgets import RadioSet, Select

class DynamicRadioSetApp(App[None]):

    def compose(self) -> ComposeResult:
        yield Select[int]((("The Beatles", 0), ("Radiohead", 1),("REM", 2)))
        with Vertical(id="band-picker"):
            yield RadioSet()

    @on(Select.Changed)
    async def pick_the_best_member(self, event: Select.Changed) -> None:
        set_container = self.query_one("#band-picker")
        await set_container.query_one(RadioSet).remove()
        members = []
        if event.value == 0:
            members = ["John", "Paul", "George", "Ringo"]
        elif event.value == 1:
            members = ["Thom", "Jonny", "Ed", "Philip"]
        elif event.value == 2:
            members = ["Bill", "Peter", "Mike", "Michael"]
        await set_container.mount(RadioSet(*members))

if __name__ == "__main__":
    DynamicRadioSetApp().run()

[davep]

Oh, and as for emit: you're looking at a pretty old issue there and it was removed almost a year back.

[lauralindzey]

Thank you so much for the comprehensive answer @davep, that makes sense!