Диалоговое окно PyQt5 python3.4

from PyQt5 import QtCore, QtGui, QtWidgets
 
class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(789, 608)
        MainWindow.setMaximumSize(QtCore.QSize(789, 608))
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.gridLayout = QtWidgets.QGridLayout(self.centralwidget)
        self.gridLayout.setObjectName("gridLayout")
        self.tabWidget = QtWidgets.QTabWidget(self.centralwidget)
        self.tabWidget.setFocusPolicy(QtCore.Qt.NoFocus)
        self.tabWidget.setContextMenuPolicy(QtCore.Qt.DefaultContextMenu)
        self.tabWidget.setObjectName("tabWidget")
        self.tab = QtWidgets.QWidget()
        self.tab_2 = QtWidgets.QWidget()
        self.tab_2.setObjectName("tab_2")
        self.pushButton_4 = QtWidgets.QPushButton(self.tab_2)
        self.pushButton_4.setGeometry(QtCore.QRect(570, 10, 81, 31))
        self.pushButton_4.setObjectName("pushButton_4")
        self.tabWidget.addTab(self.tab_2, "")
        self.gridLayout.addWidget(self.tabWidget, 0, 0, 1, 1)
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 789, 21))
        self.menubar.setObjectName("menubar")
        self.menu = QtWidgets.QMenu(self.menubar)
        self.menu.setObjectName("menu")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)
        self.action = QtWidgets.QAction(MainWindow)
        self.action.setObjectName("action")
        self.menu.addAction(self.action)
        self.menubar.addAction(self.menu.menuAction())
        self.retranslateUi(MainWindow)
        self.tabWidget.setCurrentIndex(0)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)
        self.pushButton_4.clicked.connect(lambda: exemple(self))
    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.tabWidget.setTabText(self.tabWidget.indexOf(self.tab_2), _translate("MainWindow", "Список"))
        self.menu.setTitle(_translate("MainWindow", "Файл"))
        self.action.setText(_translate("MainWindow", "Выход"))
        self.pushButton_4.setText(_translate("MainWindow", "пушБатон"))
        
def exemple(self):
    print('1')
    # Если нажата 'ok':
    #   print('True')
    #Иначе:
    #   print("False")
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_())

self.ui.button.clicked.connect(процедура)

from PyQt4 import QtGui
from PyQt4.QtGui import QApplication
from PyQt4.QtGui import QMessageBox
 
app = QApplication([])
 
msgBox = QtGui.QMessageBox()
msgBox.setStandardButtons(QMessageBox.Yes | QMessageBox.No)
msgBox.setText("Continue?")
result = msgBox.exec_()
if QMessageBox.Yes == result:
    print("yes")
elif QMessageBox.No == result:
    print("no")
else:
    print("wtf?")

# WARNING! All changes made in this file will be lost!

import sys
 
from PyQt5 import QtCore, QtWidgets
 
 
class MainWindow(QtWidgets.QWidget):
    def __init__(self):
        super(MainWindow, self).__init__()
 
        self.button_ok = None
        self.build_widgets()
 
    def build_widgets(self):
        self.setLayout(QtWidgets.QVBoxLayout())
 
        self.button_ok = QtWidgets.QPushButton('Старт')
        self.button_ok.clicked.connect(self.example)
        self.layout().addWidget(self.button_ok)
 
    def example(self):
        message = 'Вы уверены, что хотите продолжить?'
        reply = QtWidgets.QMessageBox.question(self, 'Уведомление', message,
                                               QtWidgets.QMessageBox.Yes,
                                               QtWidgets.QMessageBox.No)
 
        if reply == QtWidgets.QMessageBox.Yes:
            print('ok')
        else:
            print('cancel')
 
 
if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    window = MainWindow()
    window.show()
    sys.exit(app.exec_())