我想当QPushButton单击QLineEdit中显示的文本，但是当我单击Text按钮时，程序抛出。我做错了什么？

Question

import sys
from PyQt5.QtWidgets import (QWidget, QPushButton, QLineEdit,
    QInputDialog, QApplication)


class Example(QWidget):

    def __init__(self):
        super().__init__()

        self.initUI()


    def initUI(self):

        self.btn = QPushButton('Text', self)
        self.btn.move(20, 20)
        self.btn.clicked.connect(self.buttonClicked)

        self.le = QLineEdit(self)
        self.le.move(130, 22)

        self.setGeometry(300, 300, 290, 150)
        self.setWindowTitle('Input dialog')
        self.show()


    def buttonClicked(self):

        sender = self.sender()
        self.le.showMessage(sender.text())


if __name__ == '__main__':

    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())