QListWidget and Multiple Selection

Unfortunately I can't help with the Python specific syntax but you don't need to create any subclasses.

After your QListWidget is created, call setSelectionMode() with one of the multiple selection types passed in, probably QAbstractItemView::ExtendedSelection is the one you want. There are a few variations on this mode that you may want to look at.

In your slot for the itemSelectionChanged() signal, call selectedItems() to get a QList of QListWidgetItem pointers.

Example of getting multiple selected values in listWidget with multiple selection.

from PyQt5 import QtWidgets, QtCore
class Test(QtWidgets.QDialog):
    def __init__(self, parent=None):
        super(Test, self).__init__(parent)
        self.layout = QtWidgets.QVBoxLayout()
        self.listWidget = QtWidgets.QListWidget()
        self.listWidget.setSelectionMode(
            QtWidgets.QAbstractItemView.ExtendedSelection
        )
        self.listWidget.setGeometry(QtCore.QRect(10, 10, 211, 291))
        for i in range(10):
            item = QtWidgets.QListWidgetItem("Item %i" % i)
            self.listWidget.addItem(item)
        self.listWidget.itemClicked.connect(self.printItemText)
        self.layout.addWidget(self.listWidget)
        self.setLayout(self.layout)

    def printItemText(self):
        items = self.listWidget.selectedItems()
        x = []
        for i in range(len(items)):
            x.append(str(self.listWidget.selectedItems()[i].text()))

        print (x)

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    form = Test()
    form.show()
    app.exec_()

output :-

For PyQT4 it's

QListWidget.setSelectionMode(QtGui.QAbstractItemView.ExtendedSelection)