In the program, setText() does not display a value, why?

Question

PyQt

I wrote a simple program on the form of a button and an empty label, I want to change the text in the label by pressing the button, but something doesn’t work, tell me please ..

from PyQt5 import uic
from PyQt5 import QtWidgets
import sys

Form, Window =uic.loadUiType("untitled.ui")

class Ui (QtWidgets.QDialog, Form):
    def __init__(self):
        super(Ui, self).__init__()
        self.setupUi(self)
        self.pushButton.clicked.connect(self.printButtonPressed)

    def printButtonPressed(self):
        self.label.setText("hello")

if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    window = Window()
    form = Form()
    form.setupUi(window)
    window.show()
    app.exec()