Как вывести среднее значение из столбца QTableWidget?

• Заполните столбец.
• Кликните по заголовку столбца.
• Нажмите кнопку "Среднее значение"

from PyQt5 import QtCore, QtGui, QtWidgets

#from untitled import Ui_MainWindow
class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(640, 480)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.gridLayout = QtWidgets.QGridLayout(self.centralwidget)
        self.gridLayout.setObjectName("gridLayout")
        self.tableWidget = QtWidgets.QTableWidget(self.centralwidget)
        self.tableWidget.setObjectName("tableWidget")
        self.tableWidget.setColumnCount(6)
        self.tableWidget.setRowCount(5)
        item = QtWidgets.QTableWidgetItem()
        self.tableWidget.setVerticalHeaderItem(0, item)
        item = QtWidgets.QTableWidgetItem()
        self.tableWidget.setVerticalHeaderItem(1, item)
        item = QtWidgets.QTableWidgetItem()
        self.tableWidget.setVerticalHeaderItem(2, item)
        item = QtWidgets.QTableWidgetItem()
        self.tableWidget.setVerticalHeaderItem(3, item)
        item = QtWidgets.QTableWidgetItem()
        self.tableWidget.setVerticalHeaderItem(4, item)
        item = QtWidgets.QTableWidgetItem()
        self.tableWidget.setHorizontalHeaderItem(0, item)
        item = QtWidgets.QTableWidgetItem()
        self.tableWidget.setHorizontalHeaderItem(1, item)
        item = QtWidgets.QTableWidgetItem()
        self.tableWidget.setHorizontalHeaderItem(2, item)
        item = QtWidgets.QTableWidgetItem()
        self.tableWidget.setHorizontalHeaderItem(3, item)
        item = QtWidgets.QTableWidgetItem()
        self.tableWidget.setHorizontalHeaderItem(4, item)
        item = QtWidgets.QTableWidgetItem()
        self.tableWidget.setHorizontalHeaderItem(5, item)
        self.gridLayout.addWidget(self.tableWidget, 0, 0, 1, 1)
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton.setObjectName("pushButton")
        self.gridLayout.addWidget(self.pushButton, 1, 0, 1, 1)
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 640, 21))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        item = self.tableWidget.verticalHeaderItem(0)
        item.setText(_translate("MainWindow", "1"))
        item = self.tableWidget.verticalHeaderItem(1)
        item.setText(_translate("MainWindow", "2"))
        item = self.tableWidget.verticalHeaderItem(2)
        item.setText(_translate("MainWindow", "3"))
        item = self.tableWidget.verticalHeaderItem(3)
        item.setText(_translate("MainWindow", "4"))
        item = self.tableWidget.verticalHeaderItem(4)
        item.setText(_translate("MainWindow", "5"))
        item = self.tableWidget.horizontalHeaderItem(0)
        item.setText(_translate("MainWindow", "1"))
        item = self.tableWidget.horizontalHeaderItem(1)
        item.setText(_translate("MainWindow", "2"))
        item = self.tableWidget.horizontalHeaderItem(2)
        item.setText(_translate("MainWindow", "3"))
        item = self.tableWidget.horizontalHeaderItem(3)
        item.setText(_translate("MainWindow", "4"))
        item = self.tableWidget.horizontalHeaderItem(4)
        item.setText(_translate("MainWindow", "5"))
        item = self.tableWidget.horizontalHeaderItem(5)
        item.setText(_translate("MainWindow", "6"))
        self.pushButton.setText(_translate("MainWindow", "Среднее значение"))


class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self):
        super().__init__()
        self.setupUi(self)
  
        self.indexColumn = None
        self.pushButton.clicked.connect(self.medium)
        self.tableWidget.horizontalHeader().sectionClicked.connect(self._hh)

    def medium(self):
        rows = self.tableWidget.rowCount()

        if not self.indexColumn:
            return
            
        _sum = 0    
        for row in range(rows):  
            item = self.tableWidget.item(row, self.indexColumn)
            item = item.text() if item else '0'
            _sum += float(item) if item else 0 
        
        msg = QtWidgets.QMessageBox.information(
            self, 
           'Результат', 
           f'Среднее значение столбца {self.indexColumn} = {_sum / rows}')         
        
    def _hh(self, index):
        self.indexColumn = index
   
    
if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec_())