написал калькулятор на python (графический) не знаю как суммировать цифры

я решил написать графический калькулятор на питоне. Все сделал и взаимодействие с мышью, и с самим калькулятором даже отмена действия, но как суммировать цифры я не знаю. Можете пожалуйста помочь мне

вот код

from PySide import QtCore, QtGui
import sys
from ui import Ui_Dialog

#Creat application 
app = QtGui.QApplication(sys.argv)


#Creat from Ui and init UI
Dialog = QtGui.QDialog()
ui = Ui_Dialog()
ui.setupUi(Dialog)
Dialog.show()

#hook logic

def numbers_logic():

    def bp():
        text = ui.lineEdit.text() + "0"
        ui.lineEdit.setText(text)

    ui.pushButton_10.clicked.connect(bp)

    def bp1():
        text = ui.lineEdit.text() + "1"
        ui.lineEdit.setText(text)

    ui.pushButton.clicked.connect(bp1)

    def bp2():
        text = ui.lineEdit.text() + "2"
        ui.lineEdit.setText(text)

    ui.pushButton_2.clicked.connect(bp2)

    def bp3():
        text = ui.lineEdit.text() + "3"
        ui.lineEdit.setText(text)

    ui.pushButton_3.clicked.connect(bp3)

    def bp4():
        text = ui.lineEdit.text() + "4"
        ui.lineEdit.setText(text)

    ui.pushButton_4.clicked.connect(bp4)

    def bp5():
        text = ui.lineEdit.text() + "5"
        ui.lineEdit.setText(text)

    ui.pushButton_5.clicked.connect(bp5)

    def bp6():
        text = ui.lineEdit.text() + "6"
        ui.lineEdit.setText(text)

    ui.pushButton_6.clicked.connect(bp6)

    def bp7():
        text = ui.lineEdit.text() + "7"
        ui.lineEdit.setText(text)

    ui.pushButton_7.clicked.connect(bp7)

    def bp8():
        text = ui.lineEdit.text() + "8"
        ui.lineEdit.setText(text)

    ui.pushButton_8.clicked.connect(bp8)

    def bp9():
        text = ui.lineEdit.text() + "9"
        ui.lineEdit.setText(text)

    ui.pushButton_9.clicked.connect(bp9)

    def bp14():
        text = ui.lineEdit.text() + ","
        ui.lineEdit.setText(text)

    ui.pushButton_17.clicked.connect(bp14)


def dop():

    def bp10():
        text = ui.lineEdit.text() + "+"
        ui.lineEdit.setText(text)

    ui.pushButton_13.clicked.connect(bp10)

    def bp11():
        text = ui.lineEdit.text() + "-"
        ui.lineEdit.setText(text)

    ui.pushButton_14.clicked.connect(bp11)


    def bp12():
        text = ui.lineEdit.text() + "*"
        ui.lineEdit.setText(text)

    ui.pushButton_11.clicked.connect(bp12)

    def bp13():
        text = ui.lineEdit.text() + "/"
        ui.lineEdit.setText(text)

    ui.pushButton_12.clicked.connect(bp13)


    def bp15():
        text = ui.lineEdit.clear()
        ui.lineEdit.setText(text)  
    ui.pushButton_16.clicked.connect(bp15)

    def bp16():

        text = ui.lineEdit.text() + "="
        ui.lineEdit.setText(text)

    ui.pushButton_15.clicked.connect(bp16)





dop()
numbers_logic()

#Run mane loop
sys.exit(app.exec_())