I want to validate focus out in a QtableWidgetItem in PyQt 5?

It is not necessary to handle those events to validate a data, what you can do is use a delegate as I show below (this answer is published in for question the site in English so that it only allows you to write 2 hexadecimal digits, if you tell me that you want to validate I could give you an adequate answer for your specific question)

class HexDelegate(QItemDelegate):
    def createEditor(self, parent, option, index):
        w = QLineEdit(parent)
        w.setInputMask("HH")
        return w

class App(QWidget):
    def __init__(self, *args, **kwargs):
        QWidget.__init__(self, *args, **kwargs)
        self.setLayout(QVBoxLayout())

       # Create table
        self.tableWidget = QTableWidget(self)
        self.layout().addWidget(self.tableWidget)
        self.tableWidget.setRowCount(4)
        self.tableWidget.setColumnCount(2)
        self.tableWidget.setItemDelegate(HexDelegate())

if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = App()
    ex.show()
    sys.exit(app.exec_())