contextMenu.py

class Demo(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(Demo, self).__init__(parent)

        # initialization object
        layout = QtWidgets.QGridLayout()
        self.widget = QtWidgets.QListWidget()

        layout.addWidget(self.widget)
        self.setLayout(layout)

        self.widget.addItem('item A')
        self.widget.addItem('item B')

        self.widget.setContextMenuPolicy(QtCore.Qt.CustomContextMenu)
        self.widget.customContextMenuRequested.connect(self.openContextMenu)

        self.widget.itemClicked.connect(lambda item: self.printThings(item))

    def openContextMenu(self):
        contextMenu = QtWidgets.QMenu()

        # Enable options when only certain number of row is selected (typically one)
        selectedIndexes = list(
            set([item.row() for item in self.widget.selectedIndexes()]))
        if len(selectedIndexes) == 1:
            item = self.widget.currentItem()

            # menu option
            functionAction = contextMenu.addAction('Menu Text go here')
            functionAction.triggered.connect(
                lambda: self.execFunctionWithArgs(item))

            # menu option with sub-menu
            functionMenu = contextMenu.addMenu('More options here!')
            submenu = functionMenu.addAction('Sub Menu here')
            submenu.triggered.connect(lambda: self.execFunctionWithArgs(item))

        else:
            items = self.widget.selectedItems()

        # Enable options for other senarios
        anotherAction = contextMenu.addAction('Menu Text go here')
        anotherAction.triggered.connect(self.execFunction)

        cursor = QtGui.QCursor()
        contextMenu.exec_(cursor.pos())

    def execFunctionWithArgs(self, argument):
        pass

    def execFunction(self):
        pass

    def printThings(self, item):
        print(item)