PyQt5 TabWidget tabBarClicked TypeError: native Qt signal is not callable

Question

I am trying to making a user interface with PyQt5. If i click the 5th index tab userSettings() function will call. But program raises this error:

self.tabWidget.tabBarClicked(5).connect(self.userSettings())
TypeError: native Qt signal is not callable

How can i fix it?

import sys
import PyQt5.QtCore
from PyQt5.QtWidgets import QApplication, QMainWindow, QTabWidget, QTabBar, QWidget
from PyQt5.QtWidgets import QMessageBox
from numpy import *
from alfa_gui import Ui_MainWindow
    
class MainWindow(QMainWindow, Ui_MainWindow):

    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        QMainWindow.__init__(self)
        self.setupUi(self)
        self.tabWidget.tabBarClicked(5).connect(self.userSettings())

    def userSettings(self):
        
        if self.lineEdit.text() == "cogal" and self.lineEdit_2.text() == "cogal":
            print("Success!")
        else:
            msg = QMessageBox()
            msg.setWindowTitle("Hatalı Giriş!")
            msg.setText("Wrong Password Or Username")
            x = msg.exec_()  
            msg.setIcon(QMessageBox.Critical)

    if __name__ == '__main__':
        app = QApplication(sys.argv)
        window = MainWindow()
        window.setWindowTitle('ALFA')
        window.show()
        exit_code = app.exec_()
        sys.exit(exit_code)

Answer 1

There are two problems in your code:

1. the arguments shown in the signals documentation are the arguments received from the functions they're connected to;
2. signal connections require the reference to a callable, while you're calling the desired function (with the parentheses), which would raise a TypeError as the function returns None;

Change to:

    self.tabWidget.tabBarClicked.connect(self.userSettings)

And then:

def userSettings(self, tabIndex):
    if tabIndex != 5:
        return
    # ...

Note that you should connect to the currentChanged signal, not the tabBarClicked one, as that will be triggered anyway even if the clicked tab is already the current one.