import signal
import sys
from PySide6.QtCore import QCoreApplication, Property, QObject, Signal, Slot

class Base(QObject):
    iChanged = Signal(int)
 
    def __init__(self, i, parent=None):
        super().__init__(parent)
        self._i = i

    def getI(self):
        return self._i
 
    def setI(self, i):
        if self._i != I:
            self._i = i
            self.iChanged.emit(i)

    i = Property(int, getI, setI, notify = iChanged)


class Derived(Base):

    def__init__(self, i, parent=None):
        super().__init__(i, parent)

    def getI(self):
        return 2 * self._i
 
    # i = Property(int, getI) # Try with and without umcommenting...

@Slot(int)
def testBase(i):
    print(f'Base slot called with i = {i}')

@Slot(int)
def testDerived(i):
    print(f'Derived slot called with i = {i}')

if __name__ == '__main__':
    app = QCoreApplication(sys.argv)
    base = Base(2)
    derived = Derived(2)
    print(f'base.i = {base.i}/{base.getI()}')
    print(f'derived.i = {derived.i}/{derived.getI()}')
    base.iChanged.connect(testBase)
    derived.iChanged.connect(testDerived)
    base.setI(4)
    derived.setI(5)
    print(f'derived.i = {derived.i}/{derived.getI()}')
    signal.signal(signal.SIGINT, signal.SIG_DFL)
    sys.exit(app.exec())