[Python] Python Textual Widget not refreshing

I am new to the Textual library and I was trying to make widgets to update whenever data changes. This is a simple example of what I've tried:

class TestBody(Static):
data = reactive("")

def compose(self) -> ComposeResult:
yield Input()
yield Label(f"Data: {self.data}")

def on_input_submitted(self, message):
self.data = message.value
print("New data:", self.data)

class MyApp(App):
def compose(self) -> ComposeResult:
yield Header()
yield TestBody()
yield Footer()

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


In this example, I can type anything in the input component, and when submitted, it should be displayed by the label. But what actually happens is nothing; the label always displays "Data: ".

By using the textual console tool, I can see that the submit message is definitely being sent and picked up by my handler. I can even see the data changing in the log, but the display does not update.



I understand from the docs that I shouldn't need to use the refresh() method since I am using a reactive attribute. In any case, I tried to add self.refresh() inside on_input_submitted and it still did not work.

I have the feeling that I am missing something about this library, but I couldn't find any similar examples.

Thanks in advance.

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