One-liner with uv to try this out:

  uv run --with pywry python <<'EOF'
  app = PyWry()
  
  def on_button_click(data, event_type, label):
      """Called when the button is clicked."""
      app.emit("pywry:set-content", {"id": "greeting", "text": "Button was clicked!"}, label)
  
  html = """
  <div style="padding: 20px; text-align: center;">
      <h1 id="greeting">Click the button below</h1>
      <button onclick="window.pywry.emit('app:button-click', {time: Date.now()})">
          Click me!
      </button>
  </div>
  """
  
  app.show(
      html,
      callbacks={"app:button-click": on_button_click},
  )
  app.block()
  EOF

Looks promising. Here's a screenshot: https://gist.github.com/simonw/092386c894d3a0deb2572f3155552...