PyQt5 window is not displayed

There is the following code:

'''main.py''' import sys from PyQt5 import QtWidgets import main_window import success_window class Bot(QtWidgets.QMainWindow, main_window.Ui_MainWindow): def __init__(self): QtWidgets.QWidget.__init__(self) self.ui = main_window.Ui_MainWindow() self.ui.setupUi(self) self.ui.pushButton_2.clicked.connect(self.ship_info) def ship_info(self): success = SuccessWindow() success.show() class SuccessWindow(QtWidgets.QMainWindow,success_window.Ui_SuccessWindow): def __init__(self): QtWidgets.QWidget.__init__(self) self.ui = success_window.Ui_SuccessWindow() self.setupUi(self) def main(): app = QtWidgets.QApplication(sys.argv) window = Bot() window.show() app.exec_() if __name__ == '__main__': main() 

File success_window:

 from PyQt5 import QtCore, QtGui, QtWidgets class Ui_SuccessWindow(object): def setupUi(self, MainWindow): MainWindow.setObjectName("MainWindow") MainWindow.resize(200, 150) MainWindow.setMinimumSize(QtCore.QSize(200, 150)) MainWindow.setMaximumSize(QtCore.QSize(200, 150)) self.centralwidget = QtWidgets.QWidget(MainWindow) self.centralwidget.setObjectName("centralwidget") self.label = QtWidgets.QLabel(self.centralwidget) self.label.setGeometry(QtCore.QRect(20, 50, 161, 17)) self.label.setObjectName("label") self.pushButton = QtWidgets.QPushButton(self.centralwidget) self.pushButton.setGeometry(QtCore.QRect(50, 100, 89, 25)) self.pushButton.setObjectName("pushButton") MainWindow.setCentralWidget(self.centralwidget) self.retranslateUi(MainWindow) QtCore.QMetaObject.connectSlotsByName(MainWindow) def retranslateUi(self, MainWindow): _translate = QtCore.QCoreApplication.translate MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow")) self.label.setText(_translate("MainWindow", "Data saved successfully")) self.pushButton.setText(_translate("MainWindow", "OK")) 

Actually a question. Why is the SuccessWindow () window not displayed when I click on pushButton_2? No error occurs. The program gets into the method, but for some reason does not want to display, help.