calculator2.py

from PyQt5 import QtWidgets
import sys
from mainWindow import Ui_MainWindow

class myApp(QtWidgets.QMainWindow):
    def __init__(self):
        super(myApp,self).__init__()
        self.ui=Ui_MainWindow()
        self.ui.setupUi(self)
        self.ui.btn_toplama.clicked.connect(self.hesapla)
        self.ui.btn_cikarma.clicked.connect(self.hesapla)
        self.ui.btn_carpma.clicked.connect(self.hesapla)
        self.ui.btn_bolme.clicked.connect(self.hesapla)

    def hesapla(self):
        sender=self.sender().text() # hangi butondan tıklıyorsak o butonun referansını sender içerisine alıyoruz.

        if sender == "Toplama":
            result=int(self.ui.txt_sayi1.text())+int(self.ui.txt_sayi2.text())
        elif sender == "Çıkarma":
            result=int(self.ui.txt_sayi1.text())-int(self.ui.txt_sayi2.text())
        elif sender == "Çarpma":
            result=int(self.ui.txt_sayi1.text())*int(self.ui.txt_sayi2.text())
        elif sender == "Bölme":
            result=int(self.ui.txt_sayi1.text())/int(self.ui.txt_sayi2.text())
           
        self.ui.lbl_sonuc.setText("Sonuç: "+str(result))

def app():
    app=QtWidgets.QApplication(sys.argv)
    win=myApp()
    win.show()
    sys.exit(app.exec_())


app()