PyQt: How to set Combobox Items be Checkable?

Question

To keep the GUI widgets number to minimum I need to find a way to give to user a choice of pull-down menu items that could be used to filter out the displayed in a listWidget items. Let's say the listWidget lists 5 different categories of Items: "Cat A", "Cat B","Cat C","Cat D","Cat E". I could implement the radio or checkboxes for each item category. But then 5 radio buttons or checkboxes would take a lot of GUI space. A combobox with the checkable items seems to be a right choice. Any ideas?

from PyQt4 import QtGui, QtCore
import sys, os


class CheckableComboBox(QtGui.QComboBox):
    def __init__(self):    
        super(CheckableComboBox, self).__init__()

    def flags(self, index):
        return Qt.ItemIsUserCheckable | Qt.ItemIsSelectable | Qt.ItemIsEnabled


class Dialog_01(QtGui.QMainWindow):
    def __init__(self):
        super(QtGui.QMainWindow,self).__init__()

        myQWidget = QtGui.QWidget()
        myBoxLayout = QtGui.QVBoxLayout()
        myQWidget.setLayout(myBoxLayout)
        self.setCentralWidget(myQWidget)

        self.ComboBox = CheckableComboBox()
        for i in range(3):
            self.ComboBox.addItem("Combobox Item " + str(i))

        myBoxLayout.addWidget(self.ComboBox)


if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    dialog_1 = Dialog_01()
    dialog_1.show()
    dialog_1.resize(480,320)
    sys.exit(app.exec_())

Answer 1

This idea of a multi-select combo has come up before, but I'm not sure that its the best solution. Really, all that's needed is a tool-button with a drop-down menu (similar to the history buttons in a web-browser).

Here's a basic demo that illustrates both options (button left, combo right):

PyQt5:

from PyQt5 import QtWidgets, QtGui, QtCore

class CheckableComboBox(QtWidgets.QComboBox):
    def __init__(self):
        super(CheckableComboBox, self).__init__()
        self.view().pressed.connect(self.handleItemPressed)
        self.setModel(QtGui.QStandardItemModel(self))

    def handleItemPressed(self, index):
        item = self.model().itemFromIndex(index)
        if item.checkState() == QtCore.Qt.Checked:
            item.setCheckState(QtCore.Qt.Unchecked)
        else:
            item.setCheckState(QtCore.Qt.Checked)

class Dialog_01(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()
        myQWidget = QtWidgets.QWidget()
        myBoxLayout = QtWidgets.QHBoxLayout()
        myQWidget.setLayout(myBoxLayout)
        self.setCentralWidget(myQWidget)
        self.ComboBox = CheckableComboBox()
        self.toolbutton = QtWidgets.QToolButton(self)
        self.toolbutton.setText('Categories ')
        self.toolmenu = QtWidgets.QMenu(self)
        for i in range(3):
            self.ComboBox.addItem('Category %s' % i)
            item = self.ComboBox.model().item(i, 0)
            item.setCheckState(QtCore.Qt.Unchecked)
            action = self.toolmenu.addAction('Category %s' % i)
            action.setCheckable(True)
        self.toolbutton.setMenu(self.toolmenu)
        self.toolbutton.setPopupMode(QtWidgets.QToolButton.InstantPopup)
        myBoxLayout.addWidget(self.toolbutton)
        myBoxLayout.addWidget(self.ComboBox)

if __name__ == '__main__':

    app = QtWidgets.QApplication(['Test'])
    dialog_1 = Dialog_01()
    dialog_1.show()
    app.exec_()
    
**PyQt4**:

from PyQt4 import QtGui, QtCore

class CheckableComboBox(QtGui.QComboBox):
    def __init__(self):
        super(CheckableComboBox, self).__init__()
        self.view().pressed.connect(self.handleItemPressed)
        self.setModel(QtGui.QStandardItemModel(self))

    def handleItemPressed(self, index):
        item = self.model().itemFromIndex(index)
        if item.checkState() == QtCore.Qt.Checked:
            item.setCheckState(QtCore.Qt.Unchecked)
        else:
            item.setCheckState(QtCore.Qt.Checked)

class Dialog_01(QtGui.QMainWindow):
    def __init__(self):
        super(QtGui.QMainWindow, self).__init__()
        myQWidget = QtGui.QWidget()
        myBoxLayout = QtGui.QHBoxLayout()
        myQWidget.setLayout(myBoxLayout)
        self.setCentralWidget(myQWidget)
        self.ComboBox = CheckableComboBox()
        self.toolbutton = QtGui.QToolButton(self)
        self.toolbutton.setText('Categories ')
        self.toolmenu = QtGui.QMenu(self)
        self.toolbutton.setMenu(self.toolmenu)
        self.toolbutton.setPopupMode(QtGui.QToolButton.InstantPopup)
        for i in range(3):
            self.ComboBox.addItem('Category %s' % i)
            item = self.ComboBox.model().item(i, 0)
            item.setCheckState(QtCore.Qt.Unchecked)
            action = self.toolmenu.addAction('Category %s' % i)
            action.setCheckable(True)
        myBoxLayout.addWidget(self.toolbutton)
        myBoxLayout.addWidget(self.ComboBox)

if __name__ == '__main__':

    app = QtGui.QApplication(['Test'])
    dialog_1 = Dialog_01()
    dialog_1.show()
    app.exec_()

Answer 2

It is very easy. Just set the item Checkable using the flags() function in the model associated with the comboBox.

def flags(self, index):
    return Qt.ItemIsUserCheckable | Qt.ItemIsSelectable | Qt.ItemIsEnabled

UPDATE

---

This may not be the best method, But it should sort your problem. Here is a something u may want look at , IF you have space restrictionn and cannot display the complete listView, Just resize it until it looks like a ComboBox.