I studied QML with signal-slot communication across to Python a bit.
If you are looking for examples in source code, see
This video shows a very small application, consisting of two files - webview.qml and webview-qml.py.
The first three signals originate from QML and Python opens up a QMessageBox to display them, along by printing to stdout. The third signal will emit a fourth signal from Python to QML, with an url as a parameter, and the url will open inside a WebView.
This app evolves the idea a bit further. The HTML5 canvas demos seen in the video are not by me, they are from the web. There is a state machine working behind the scenes.