Resources: Python-GUI-PyQ5 general overview.xmind；QObject.xmind

1, destroyed(obj): this signal is sent when the object is destroyed (widget. Signal. Connect: connect signal and slot)

from PyQt5.Qt import *
class Window(QWidget):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("QObject Learning")  # Window title
        self.resize(500, 500)  # Set window size
        self.setup_ui()

    def setup_ui(self):
        self.QObject Operation of signals()

    def QObject Operation of signals(self):
        self.obj=QObject()  #self means Window, which will not be released

        def destroy_cao(obj):   #Listening for obj 2 object is released
            print("obj2 Object is released",obj)
        self.obj.destroyed.connect(destroy_cao)  #There is no print here: "object2 object is released < pyqt5. Qtcore. QObject object at 0x00000204e0f7d310 >"

        del self.obj  #Here print "object 2 is released < pyqt5. Qtcore. QObject object at 0x00000204e0f7d310 >"

if __name__ == '__main__':
    import sys
    app = QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())

2, Objectname changed (objectname): this signal is emitted when the object name changes

from PyQt5.Qt import *
class Window(QWidget):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("QObject Learning")  # Window title
        self.resize(500, 500)  # Set window size
        self.setup_ui()

    def setup_ui(self):
        self.QObject Operation of signals()

    def QObject Operation of signals(self):
        self.obj=QObject()
        def obj_name_cao(name):
            print("Object name changed",name)

        self.obj.objectNameChanged.connect(obj_name_cao)
        self.obj.setObjectName("666")

if __name__ == '__main__':
    import sys
    app = QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())

#Return
'''
//Object name changed 666
'''

3, obj.disconnect(): disconnect signal from slot.

obj: control > cancel all signal connections of the control, signal > cancel the connection of the specified signal

from PyQt5.Qt import *
class Window(QWidget):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("QObject Learning")  # Window title
        self.resize(500, 500)  # Set window size
        self.setup_ui()

    def setup_ui(self):
        self.QObject Operation of signals()

    def QObject Operation of signals(self):
        self.obj=QObject()
        def obj_name_cao(name):
            print("Object name changed",name)

        self.obj.objectNameChanged.connect(obj_name_cao)
        self.obj.setObjectName("666")
        self.obj.objectNameChanged.disconnect(obj_name_cao)  #Although the signal is triggered, the signal is disconnected from the slot
        self.obj.setObjectName("888")

if __name__ == '__main__':
    import sys
    app = QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())

#Return
'''
//Object name changed 666
'''

4, widget.blockSignals(bool): temporarily (cancel) the connection between all signals of the control and the slot

from PyQt5.Qt import *
class Window(QWidget):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("QObject Learning")  # Window title
        self.resize(500, 500)  # Set window size
        self.setup_ui()

    def setup_ui(self):
        self.QObject Operation of signals()

    def QObject Operation of signals(self):
        self.obj=QObject()
        def obj_name_cao(name):
            print("Object name changed",name)

        self.obj.objectNameChanged.connect(obj_name_cao)
        self.obj.setObjectName("666")
        self.obj.blockSignals(True)  #Temporary block
        self.obj.setObjectName("888")
        self.obj.blockSignals(False)
        self.obj.setObjectName("777")

if __name__ == '__main__':
    import sys
    app = QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())

#Return
'''
//Object name changed 666
//Object name changed 777
'''

5, widget.signalsBlocked(): whether the signal is blocked

from PyQt5.Qt import *
class Window(QWidget):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("QObject Learning")  # Window title
        self.resize(500, 500)  # Set window size
        self.setup_ui()

    def setup_ui(self):
        self.QObject Operation of signals()

    def QObject Operation of signals(self):
        self.obj=QObject()
        def obj_name_cao(name):
            print("Object name changed",name)

        self.obj.objectNameChanged.connect(obj_name_cao)
        self.obj.setObjectName("666")
        print(self.obj.signalsBlocked(),"1")

        self.obj.blockSignals(True)  #Temporary block
        print(self.obj.signalsBlocked(),"2")
        self.obj.setObjectName("888")

        self.obj.blockSignals(False)  #Reply connection
        print(self.obj.signalsBlocked(),"3")
        self.obj.setObjectName("777")

if __name__ == '__main__':
    import sys
    app = QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())

#Return
'''
//Object name changed 666
False 1
True 2
False 3
//Object name changed 777
'''

6, Widget. Receivers: returns the number of receivers connected to the signal

from PyQt5.Qt import *
class Window(QWidget):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("QObject Learning")  # Window title
        self.resize(500, 500)  # Set window size
        self.setup_ui()

    def setup_ui(self):
        self.QObject Operation of signals()

    def QObject Operation of signals(self):
        self.obj=QObject()
        def obj_name_cao(name):
            print("Object name changed 1",name)

        def obj_name_cao2(name):
            print("Object name changed 2",name)

        self.obj.objectNameChanged.connect(obj_name_cao)
        self.obj.objectNameChanged.connect(obj_name_cao2)

        print(self.obj.receivers(self.obj.objectNameCAhanged))

        self.obj.setObjectName("666")

if __name__ == '__main__':
    import sys
    app = QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())

#Return
'''
2
//Object name changed 1 666
//Object name changed 666
'''