python pyqt5显示一段数字

import numpy as np
import math
from cv2 import cv2 as cv
from PyQt5 import QtCore, QtGui, QtWidgets
import sys

def psnr(img_1, img_2):
    mse = np.mean((img_1 / 1.0 - img_2 / 1.0) ** 2)
    if mse < 1.0e-10:
        return 100
    return 10 * math.log10(255.0 ** 2 / mse)

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(800, 600)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton.setGeometry(QtCore.QRect(220, 100, 93, 28))
        self.pushButton.setObjectName("pushButton")
        self.lineEdit = QtWidgets.QLineEdit(self.centralwidget)
        self.lineEdit.setGeometry(QtCore.QRect(250, 180, 113, 21))
        self.lineEdit.setObjectName("lineEdit")
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 26))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

        self.pushButton.clicked.connect(self.check_PSNR)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.pushButton.setText(_translate("MainWindow", "PushButton"))

    def check_PSNR(self):
        imgCoverPath = 'D:/study/Python/Python_PyCharm_Project/MHero/img/Embed.bmp'
        imgStegoPath = 'D:/study/Python/Python_PyCharm_Project/MHero/img/abc.bmp'
        imgCover = cv.imread(imgCoverPath, cv.IMREAD_UNCHANGED)
        imgStego = cv.imread(imgStegoPath, cv.IMREAD_UNCHANGED)
        print(psnr(imgCover, imgStego))
        self.lineEdit.setText(psnr(imgCover, imgStego))


if __name__ == "__main__":

    app = QtWidgets.QApplication(sys.argv)
    formObj = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(formObj)
    formObj.show()
    sys.exit(app.exec_())

运行点击按钮后出现闪退，我想把控制台的那串数字通过点击事件后显示在框内需要怎么写？求教，谢谢！！！

sys.exit(app.exec_())
把这个去掉看看

self.lineEdit.setText(psnr(imgCover, imgStego))
->
self.lineEdit.setText(str(psnr(imgCover, imgStego)))