Widget

import sys
from PyQt5.QtGui import  *
from PyQt5.QtWidgets import (QApplication, QPushButton, QLabel,
                             QGridLayout, QHBoxLayout, QDialog, QButtonGroup,
                             QTextBrowser, QLineEdit)

class MyApp(QDialog): 
    def __init__(self):
        super().__init__()
        self.title = 'PushPop'
        self.initializeUI()
        self.text = ""
        self.stack = []
        global length
        length = len(self.stack)
        #print(length)
    def initializeUI(self):
        #length = 0
        
        
        
        self.setWindowTitle(self.title)
        self.number1 = QPushButton("Push")
        self.number2 = QPushButton("Pop")
        self.number3 = QPushButton("Clear")
        self.TextB = QTextBrowser()
        self.QLineEdit = QLineEdit()
        self.QLineEdit.setStyleSheet('background-color: white')
        self.label2 = QLabel('Size: ')
        self.label2.setStyleSheet('background-color: white')
        self.label3 = QLabel('Message: ')
        self.label3.setStyleSheet('background-color: white')
        
        
        layout = QGridLayout()
        layout.addWidget(self.QLineEdit,0,0,1,6)
        layout.addWidget(self.TextB,1,1,5,5)
        layout.addWidget(self.number1,0,6)
        layout.addWidget(self.number2,1,6)
        layout.addWidget(self.number3,2,6)
        layout.addWidget(self.label2,6,0,3,6)
        layout.addWidget(self.label3,10,0,3,6)
   
    
        self.setLayout(layout)
    
        self.PushPop = QButtonGroup()
        
        self.PushPop.addButton(self.number1)
        self.PushPop.addButton(self.number2)
        self.PushPop.addButton(self.number3)
        
        
        self.PushPop.buttonClicked.connect(self.on_click)
        
        
        
        self.show()

    def on_click(self,btn):
       if (btn.text()) == "Push":
           self.stack.append(self.QLineEdit.text())
           temp = self.stack.copy()
           temp.reverse()

           #self.stack = self.stack[::-1]
           
           #self.TextB.append(self.QLineEdit.text())
           self.TextB.clear()
           for item in temp:
               self.TextB.append(item)
           
           
           self.label2.setText('Size: ' + str(len(self.stack)))
           self.label3.setText("Pushed")
       
       elif len(self.stack) == 0:
           pass
       
       elif (btn.text()) == "Pop":
           self.stack.pop()
           self.label2.setText('Size: ' + str(len(self.stack)))
           self.label3.setText("Popped")
       
        
           self.TextB.clear()
           
           temp = self.stack.copy()
           temp.reverse()
           for x in temp:
               self.TextB.append(x)
       
       elif (btn.text()) == "Clear":
           self.stack.clear()
           self.TextB.clear()
           self.label3.setText("Stack Cleared")
           self.label2.setText('Size: ' + str(len(self.stack)))
           
           #self.TextB.append(stack)
           #print(self.stack)
           
       
   

    
app = QApplication(sys.argv)
ex = MyApp()
sys.exit(app.exec_())