Squish uses QMetaOjbect to find properties and slots. In order for Python data members of QObject-derived classes to be exposed as Qt Properties, you must expose them with the PyQt5.QtCore.pyqtProperty(...) decorator. Likewise, for Python methods to be exposed as 'slots', they must be marked as slots with PyQt5.QtCore.pyqtSlot(...) .
More details can be found here: