How to make a QComboBox group mutually exclusive?

Question

Once an item is selected on a combo, it should get removed from the others, unless it's "No use".

I made three options of QComboBox, and each of those contains the same items.

The explanation is this:

• QCombobox Tug 1 has total 4 items ('No Use', '207HR', '306DR', 'Jupiter')

• QCombobox Tug 2 has total 4 items ('No Use', '207HR', '306DR', 'Jupiter')

• QCombobox Tug 3 has total 4 items ('No Use', '207HR', '306DR', 'Jupiter')

The default value of those Qcombobox is 'No Use'.

How can I remove the selected value of QComboBox Tug 1 from QComboBox Tug 2?

The point is that 'No Use' shall not be removed; only an item from among '207HR', '306DR', and 'Jupiter'.

The Code i made is below:

class Ship_Use_Tug_Input_Program(QWidget):
    def __init__(self, master):
        super().__init__()
        self.initUI()

    def initUI(self):
        tug1_cb = QComboBox(self)
        jeju_tug = ['No use','207HR (2,500HP)', '306DR (3,600HP)', 'Jupiter (3,600HP)']
        tug1_cb.addItems(jeju_tug)

        tug2_cb = QComboBox(self)
        tug2_cb.addItems(jeju_tug)

        tug3_cb = QComboBox(self)
        tug3_cb.addItems(jeju_tug)

        self.setGeometry(100,100,1000,500) 
        self.setWindowTitle('Ship_Use_Tug_Input_Program')
        self.show()
app = QApplication(sys.argv)
exc = Ship_Use_Tug_Input_Program(master=Ship_Use_Tug_Input_Program)
app.exec_()

The explanation photo is below:

Answer 1

The view-widget of the combo-box can be used to hide the rows, and the item-data can be used to keep track of which combo-box is showing which row. A slot connected to the activated signal can then update the items whenever one of the current-items change.

Below is a complete demo script that implements that. The ExclusiveComboGroup class can be used with any group of combo-boxes. To use it, just create an instance and then add all your combo-boxes using its addCombo method.

Demo Script :

import sys
from PyQt5.QtCore import *
from PyQt5.QtWidgets import *

class ExclusiveComboGroup(QObject):
    def __init__(self, parent=None):
        super().__init__(parent)
        self._combos = []
        self._role = Qt.UserRole + 500

    def addCombo(self, combo):
        combo.activated.connect(
            lambda: self.handleActivated(combo))
        self._combos.append(combo)

    def handleActivated(self, target):
        index = target.currentIndex()
        groupid = id(target)
        for combo in self._combos:
            if combo is target:
                continue
            previous = combo.findData(groupid, self._role)
            if previous >= 0:
                combo.view().setRowHidden(previous, False)
                combo.setItemData(previous, None, self._role)
            if index > 0:
                combo.setItemData(index, groupid, self._role)
                combo.view().setRowHidden(index, True)

class Window(QWidget):
    def __init__(self):
        super().__init__()
        self.group = QGroupBox('Selected Tug')
        layout = QVBoxLayout(self)
        layout.addWidget(self.group)
        layout = QFormLayout(self.group)
        layout.setVerticalSpacing(15)
        layout.setHorizontalSpacing(50)
        jeju_tug = [
            'No use',
            '207HR (2,500HP)',
            '306DR (3,600HP)',
            'Jupiter (3,600HP)',
            ]
        # create a combo-group
        self.tugs = ExclusiveComboGroup(self)
        for index in range(3):
            combo = QComboBox(self)
            combo.addItems(jeju_tug)
            layout.addRow(f'Tug {index + 1}', combo)
            # add the combo-box
            self.tugs.addCombo(combo)

if __name__ == "__main__":

    app = QApplication(sys.argv)
    window = Window()
    window.setWindowTitle('Demo')
    window.setGeometry(800, 200, 100, 50)
    window.show()
    sys.exit(app.exec_())

---

PS : here is how to use it in your own example:

def initUI(self):
    tug1_cb = QComboBox(self)
    jeju_tug = ['No use','207HR (2,500HP)', '306DR (3,600HP)', 'Jupiter (3,600HP)']
    tug1_cb.addItems(jeju_tug)

    tug2_cb = QComboBox(self)
    tug2_cb.addItems(jeju_tug)

    tug3_cb = QComboBox(self)
    tug3_cb.addItems(jeju_tug)
    
    # copy the ExclusiveComboGroup class into
    # your code and then add this section
    tugs = ExclusiveComboGroup(self)
    tugs.addCombo(tug1_cb)
    tugs.addCombo(tug2_cb)
    tugs.addCombo(tug3_cb)