[Python] Login Button in Qt Designer

I created a login interface in Qt Designer and when I converted it to Python code and ran it, everything looked just fine up until I clicked the log-in button and that was when the program just ended without running the function that I created which was supposed to pop up a message box when the user either correctly inputs a validated email and password or if they incorrectly input one as well.

This is the code that I currently have:

import sys
import re
from PyQt5 import QtWidgets
from PyQt5.QtWidgets import QMessageBox, QApplication, QMainWindow, QLineEdit
from PyQt5.uic import loadUi



class Login(QMainWindow):
def __init__(self):
super(Login, self).__init__()
loadUi("login2.ui", self)

self.loginbutton.clicked.connect(self.loginfunction)
# Cover the password input
self.passwordentry.setEchoMode(QLineEdit.Password)

def loginfunction(self):
email = self.email.text()
password = self.passwordentry.text()

if not self.validate_email(email):
QMessageBox.warning(self, "Invalid Email", "Please enter a valid email address.")
return

if not self.validate_password(password):
QMessageBox.warning(self, "Invalid Password", "Password must meet the following requirements:\n"
"- Minimum 8 characters\n"
"- At least one lowercase letter\n"
"- At least one uppercase letter\n"
"- At least one digit\n"
"- At least one special character (_@$).")
return

QMessageBox.information(self, "Login Success", "You have successfully logged in!")

@staticmethod
def validate_email(email):
pattern = r'^[a-zA-Z0-9_-]+@[a-zA-Z0-9]+\.[a-zA-Z]{1,3}$'
return re.fullmatch(pattern, email) is not None

@staticmethod
def validate_password(password):
if len(password) < 8:
return False
if not any(char.islower() for char in password):
return False
if not any(char.isupper() for char in password):
return False
if not any(char.isdigit() for char in password):
return False
if not any(char in "_@$" for char in password):
return False
return True


app = QApplication(sys.argv)
mainwindow = Login()
mainwindow.show()
widget = QtWidgets.QStackedWidget()
widget.addWidget(mainwindow)
widget.setFixedWidth(600)
widget.setFixedHeight(800)
widget.show()
app.exec_()


This is what the program looks like:

A screenshot of the properties for the login button in Qt Designer:



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