pyqt/designer/compiled_example.py

import os.path
import random
import sys

from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import QApplication, QMainWindow

from MainWindow import Ui_MainWindow

basedir = os.path.dirname(__file__)


class MainWindow(QMainWindow, Ui_MainWindow):
    def __init__(self):
        super().__init__()
        self.setupUi(self)

        f = self.label.font()
        f.setPointSize(25)
        self.label.setAlignment(Qt.AlignHCenter | Qt.AlignVCenter)
        self.label.setFont(f)

        self.pushButton.pressed.connect(self.update_label)

    def update_label(self):
        n = random.randint(1, 6)
        self.label.setText("%d" % n)


app = QApplication(sys.argv)
window = MainWindow()
window.show()
app.exec_()