t.out

connect returned: <__main__.Connection object at 0x7f6f954132e8>
entered b

t.py

import signal
import sys

from PyQt5 import QtCore, QtWidgets


def sigint_handler(signal_number, stack_frame):
    QtWidgets.QApplication.exit(128 + signal_number)


def setup_sigint():
    signal.signal(signal.SIGINT, sigint_handler)

    # Regularly give Python a chance to receive signals such as ctrl+c
    timer = QtCore.QTimer()
    timer.start(200)
    timer.timeout.connect(lambda: None)

    return timer


class Connection:
    def __init__(self, signal, slot):
        signal.connect(slot)
        self.signal = signal
        self.slot = slot
    
    def disconnect(self):
        self.signal.disconnect(self.slot)


class DynamicThing(QtCore.QObject):
    signal = QtCore.pyqtSignal()
    
    def do_it(self):
        self.signal.emit()


class Gui(QtCore.QObject):
    transition_signal = QtCore.pyqtSignal()

    def __init__(self, parent=None):
        super().__init__(parent)

        self.machine = QtCore.QStateMachine()

        self.state_a = QtCore.QState()
        self.machine.addState(self.state_a)

        self.state_b = QtCore.QState()
        self.machine.addState(self.state_b)
        
        self.state_a.addTransition(self.transition_signal, self.state_b)
        
        self.machine.setInitialState(self.state_a)

        self.state_b.entered.connect(lambda: print('entered b'))
        
        self.machine.start()
    
    def do_dynamic_thing(self):
        dynamic = DynamicThing()
        saved_connection = Connection(dynamic.signal, self.transition_signal)
        #saved_connection = QtCore.QObject.connect(dynamic, signal, self, transition_signal)
        print('connect returned:', repr(saved_connection))

        dynamic.do_it()

        #dynamic.signal.disconnect(self.transition_signal)
        saved_connection.disconnect()

app = QtWidgets.QApplication(sys.argv)

sigint_timer = setup_sigint()

gui = Gui()
QtCore.QTimer.singleShot(2000, gui.do_dynamic_thing)
QtCore.QTimer.singleShot(3000, app.exit)

app.exec()