Pyqt Prevent Combobox Change Value

I have four combo-box boxes that in PyQT4. If user change the value in first combo-box the values from second are altered and similarly if the value in second combo-box change, tha

Solution 1:

To prevent an object from issuing signals in a given context you must use blockSignals():

bool QObject.blockSignals (self, bool b)

If block is true, signals emitted by this object are blocked (i.e., emitting a signal will not invoke anything connected to it). If block is false, no such blocking will occur.

The return value is the previous value of signalsBlocked().

Note that the destroyed() signal will be emitted even if the signals for this object have been blocked.

To simplify the task, the setCurrentIndex() method will be overwritten.

classComboBox(QComboBox):
    defsetCurrentIndex(self, ix):
        self.blockSignals(True)
        QComboBox.setCurrentIndex(self, ix)
        self.blockSignals(False)

The following example shows its use:

class Widget(QWidget):
    def __init__(self, parent=None):
        QWidget.__init__(self, parent)
        self.setLayout(QVBoxLayout())

        l = [str(i) for i in range(5)]
        cb1 = ComboBox(self)
        cb1.addItems(l)

        cb2 = ComboBox(self)
        cb2.addItems(l)

        cb3 = ComboBox(self)
        cb3.addItems(l)

        cb4 = ComboBox(self)
        cb4.addItems(l)

        cb1.currentIndexChanged.connect(cb2.setCurrentIndex)
        cb2.currentIndexChanged.connect(cb3.setCurrentIndex)
        cb3.currentIndexChanged.connect(cb4.setCurrentIndex)

        self.layout().addWidget(cb1)
        self.layout().addWidget(cb2)
        self.layout().addWidget(cb3)
        self.layout().addWidget(cb4)

if __name__ == '__main__':
    app = QApplication(sys.argv)
    w = Widget()
    w.show()
    sys.exit(app.exec_())

Solution 2:

I cannot provide you exact code but conceptually you can set some flag at global level and when you don't want event to trigger you can simply return function call without at first line

Probably something like this

Boolean flag3rdCombo  = false;

functiononchangesecondCombo(){

    if (flag3rdCombo){
        return;
    }

    .....

}