如何使用PyQt5更改同一窗口中的UI？

from PyQt5.QtWidgets import QApplication, QMainWindow, QPushButton, QLabel

class MyWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        self.setWindowTitle("UI示例")
        self.setGeometry(100, 100, 300, 200)

        self.label = QLabel("初始文本", self)
        self.label.move(50, 50)

        self.button = QPushButton("点击修改文本", self)
        self.button.move(50, 100)
        self.button.clicked.connect(self.changeText)

    def changeText(self):
        self.label.setText("修改后的文本")

if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = MyWindow()
    window.show()
    sys.exit(app.exec_())