Python报错——AttributeError: module 'PyQt5.QtGui' has no attribute 'QApplication'

Python报错——AttributeError: module ‘PyQt5.QtGui’ has no attribute ‘QApplication’

初次用Python制作图形界面，遇到了这个问题

AttributeError: module ‘PyQt5.QtGui’ has no attribute ‘QApplication’

代码如下：

from PyQt5 import QtCore, QtGui, QtWidgets
class Ui_MainWindow(object):
def setupUi(self, MainWindow):
MainWindow.setObjectName("MainWindow")
MainWindow.resize(520, 401)
self.centralwidget = QtWidgets.QWidget(MainWindow)
self.centralwidget.setObjectName("centralwidget")
self.quitButton = QtWidgets.QPushButton(self.centralwidget)
self.quitButton.setGeometry(QtCore.QRect(350, 260, 91, 51))
self.quitButton.setAutoDefault(False)
self.quitButton.setDefault(False)
self.quitButton.setFlat(False)
self.quitButton.setObjectName("quitButton")
MainWindow.setCentralWidget(self.centralwidget)
self.menubar = QtWidgets.QMenuBar(MainWindow)
self.menubar.setGeometry(QtCore.QRect(0, 0, 520, 23))
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)

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

if __name__ == "__main__":
import sys
app=QtWidgets.QApplicatio
4000
n(sys.argv)
widget=QtWidgets.QWidget()
ui=Ui_MainWindow()
ui.setupUi(widget)
widget.show()
sys.exit(app.exec_())

查了一些资料后发现：我用qt designer创建的是一个mainwindow，而不是wideget或者dialog,所以需要把

app=QtWidgets.QApplication(sys.argv)

改成

widget=QtWidgets.QMainWindow()

然后界面就出来啦~~~