Python – Qcombobox in PyQt, how to set options in one combo box based on the choice of other combo boxes?

For example, the first combo box with option A and option B.
If I select option A in the first combo box, the second combo box contains options 1, 2, 3, 4, 5.
If I select option B in the first combo box, the second combo box contains options a, b, c, d, e.

How can I do this in PyQt5? I searched for the Qcombobox class and there are 2 classes activated and currentIndexChanged, but don’t know which one I need to use in PyQt5 and how to use it.

I’ll do it :

import sys
from PyQt5 import QtWidgets

class ComboWidget(QtWidgets.QWidget):

def __init__(self, parent=None):
        super(ComboWidget, self).__init__(parent)
        self.setGeometry(50, 50, 200, 200)

layout = QtWidgets.QVBoxLayout(self)

self.comboA = QtWidgets.QComboBox()
        # The second addItem parameter is itemData, which we will retrieve later
        self.comboA.addItem('A', ['1', '2', '3', '4'])
        self.comboA.addItem('B', ['a', 'b', 'c', 'd', 'e'])
        self.comboA.currentIndexChanged.connect(self.indexChanged)
        layout.addWidget(self.comboA)

self.comboB = QtWidgets.QComboBox()
        # We could have added the 1,2,3,4 items directly, but the following
        # is a bit more generic in case the combobox starts with a different
        # index for some reason:
        self.indexChanged(self.comboA.currentIndex())
        layout.addWidget(self.comboB)

self.show()

def indexChanged(self, index):
        self.comboB.clear()
        data = self.comboA.itemData(index)
        if data is not None:
            self.comboB.addItems(data)

def main():
    app = QtWidgets.QApplication(sys.argv)
    w = ComboWidget()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()

This way, your code is more forward-looking, because it makes it very easy to add/modify/remove items from any drop-down menu if you want to add/modify/remove items at some point.