parallel textual lists

myapp.py

from textual.app import App, ComposeResult
from textual.widgets import ListView, ListItem, Label
from textual.containers import Horizontal, Container
from textual.widget import Widget
from textual.reactive import reactive

class Child(Widget):
    def __init__(self, parent_widget,**kwargs):
        super().__init__(**kwargs)
        self.parent_widget = parent_widget

    def compose(self) -> ComposeResult:
        species = [ListItem(Label(item)) for item in ["cat","dog"]]
        self.species_view = ListView(*species)
        yield self.species_view

    def update_species(self, kingdom):
        if kingdom == "Animal":
            species = ["cat", "dog"]
        else:
            species = ["palm", "olive tree"]
        
        # Clear existing items
        self.species_view.clear()
        
        # Add new items to existing ListView
        for item in species:
            self.species_view.append(ListItem(Label(item)))

class TUI(App):
    active_kingdom = reactive("Animal")
    def __init__(self) -> None:
        super().__init__()
        self.kingdom_view = ListView()

    def compose(self) -> ComposeResult:
        """Create children for layout"""
        kingdoms = [ListItem(Label(item)) for item in ["Animal", "Plant"]]
        self.kingdom_view = ListView(*kingdoms)
        self.species_view = Child(self.active_kingdom)
        yield Horizontal(
            Container(self.kingdom_view),
            Container(self.species_view)
        )

    def on_list_view_highlighted(self, message: ListView.Highlighted) -> None:
            self.active_kingdom = message.item
            self.species_view.update_species(self.active_kingdom)

if __name__ == "__main__":
    app = TUI()
    app.run()