PyQt5 How to assign text from QLineEdit to variable?

Question

Python

I'm making a big application, everything hangs on the line a = self.lineEdit_1.toPlainText(), now I'm trying to make a small program with only this function to understand what's going on, but then everything crashes on the same line.
We need to assign the text from lineEdit_1 to the variable a, then display the text of variable a in lineEdit_2.
What am I doing wrong?( Thanks in advance for your help :)

from PyQt5 import QtCore, QtGui, QtWidgets

class MyWin(QtWidgets.QMainWindow):
       
    def __init__(self, parent=None):
        QtWidgets.QWidget.__init__(self, parent)
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)
        self.ui.pushButton.clicked.connect(self.btnClicked)
    def btnClicked(self):
        a = self.lineEdit_1.toPlainText()
        self.ui.lineEdit_2.setPlainText(a)
app = QtWidgets.QApplication([])
application = MyWin()
application.show()
 
sys.exit(app.exec())       
if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

Answer 1

QLineEdit does not have setPlainText and toPlainText functions, use setText and text