numbers_app.py

from textual.app import App
from textual.reactive import reactive
from textual.widget import Widget
from textual.widgets import Footer, Header, Input, Label, ListItem, ListView, Static

"""
My naive expectation was that, when I update Numbers#term, the ListView would
re-render. But it doesn't. 

I am almost positive I understand why. If term was used in a render method, it would smart refresh.

And I know how to make it work like I want manually, or with a watch method. 
But I'm wondering if there's a more idiomatic way to do this.
"""

class NumbersApp(App):
    CSS_PATH = "main.css"

    def compose(self):
        yield Header()
        yield SearchTerm()
        yield Numbers()
        yield Footer()

    def on_input_submitted(self, event):
        val = self.query_one(Input).value
        self.query_one(Numbers).search(int(val))


class Numbers(Widget):
    term = reactive(1)

    def compose(self):
        yield Static(f"Term: {self.term}")
        list_items = [ListItem(Label(x)) for x in self.get_number_rows()]
        yield ListView(*list_items)

    def search(self, val):
        self.term = val

    def get_number_rows(self):
        res = [f"Num: {x}" for x in range(100) if x % self.term == 0]
        return res[:20]


class SearchTerm(Widget):
    def compose(self):
        yield Static("search")
        yield Input()


NumbersApp().run()