How to customize a ListItem widget?

[Tim-Cao]

from typing import Optional

from textual.app import App, ComposeResult
from textual.widgets import *
from textual.widgets import *


class MenuItem(ListItem):
    def __init__(self, name: Optional[str] = None, id: Optional[str] = None) -> None:
        super().__init__()
        self.name = name
        self.id = id

    def compose(self) -> ComposeResult:
        yield Text(self.name, self.id)


class Text(Static):
    pass


class Demo(App[None]):
    def compose(self) -> ComposeResult:
        yield Header()
        yield ListView(MenuItem("Text Item", "nav-1"))
        yield Footer()


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

When do it in this way, I met this error. Could anyone help me? Thanks

[davep]

There's a couple of different problems with your code. First off, Textual widgets have a name and an id property anyway, so if you're overriding the __init__ and you want to use those you'll need to pass them to the super().__init__ call. Secondly, when you instantiate your Text widget, which inherits from Static, you're passing more positional arguments than Static's __init__ is designed to take; it has only the one positional argument, the rest are keyword arguments.

A clean starting point for your code would be something like this:

from textual.app import App, ComposeResult
from textual.widgets import Static, ListView, ListItem, Header, Footer


class Demo(App[None]):
    def compose(self) -> ComposeResult:
        yield Header()
        yield ListView(ListItem(Static("Text Item", id="nav-1")))
        yield Footer()


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

Assuming you want to add to what you were trying to do, but this was a basic example, a starting point more akin to what you were doing might be this:

from textual.app import App, ComposeResult
from textual.widgets import Static, ListView, ListItem, Header, Footer


class Text(Static):
    pass


class MenuItem(ListItem):

    def __init__(self, text: str, id: str | None = None) -> None:
        super().__init__(id=id)
        self._text = text

    def compose(self) -> ComposeResult:
        yield Text(self._text, id=self.id)


class Demo(App[None]):

    def compose(self) -> ComposeResult:
        yield Header()
        yield ListView(MenuItem("Text Item", "nav-1"))
        yield Footer()


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

[Tim-Cao]

How to know which is positional argument?

[davep]

Anything before the * in the above would be positional¹; anything after would be keyword-only. You can read more about this notation in the standard Python documentation.

Footnotes

1. Technically optionally a keyword too but that's not important here. ↩

[Tim-Cao]

I see. Thanks @davep