Python PyQt5 QMessageBox not opening

Question

I am trying to open a Message Box when I press the infoButton. It runs the infoDialogue method because it prints "I'm here" but it doesn't open the infoBox. What I'm missing?

I'm using python 3.5 with PyQt5

Thanks!

Here's the code:

import sys
from PyQt5.QtWidgets import (QApplication, QWidget, QToolTip, QPushButton, QMessageBox)
from PyQt5.QtCore import QCoreApplication
from PyQt5.QtGui import QIcon, QFont

class mainWindow(QWidget):

    def __init__(self, screenWidth, screenHeight, windowWidth=400, windowHeight=400):      
        super().__init__()
        self.screenWidth = screenWidth
        self.screenHeight = screenHeight              
        self.windowWidth = windowWidth
        self.windowHeight = windowHeight
        self.initUI()


    def initUI(self):
        QToolTip.setFont(QFont('SansSerif', 10))
        self.setToolTip('ToolTip Widget')

        exitButton = QPushButton('Exit', self)        
        exitButton.setToolTip("<b>Wish to Exit?</b>")        
        exitButton.resize(exitButton.sizeHint())       
        exitButton.move(100, 100)      
        exitButton.clicked.connect(QCoreApplication.instance().quit)           

        infoButton = QPushButton('Info', self) # Button that calls infoDialogue()
        infoButton.setToolTip('<b>ToolTip</b>')
        infoButton.resize(infoButton.sizeHint())
        infoButton.move(100, 200)
        infoButton.clicked.connect(self.infoDialogue)      

        positionX = (self.screenWidth - self.windowWidth) / 2
        positionY = (self.screenHeight - self.windowHeight) / 2
        self.setGeometry(positionX, positionY, self.windowWidth, self.windowHeight)

        self.setWindowTitle('Window Title')
        #self.setWindowIcon(QIcon('./icon.png'))

        self.show()


    def infoDialogue(self): ## Method to open a message box
        infoBox = QMessageBox() ##Message Box that doesn't run
        print("Im here")
        infoBox.setIcon(QMessageBox.Information)
        infoBox.setText("Informações Adicionais")
        infoBox.setInformativeText("Informative Text")
        infoBox.setWindowTitle("Window Title")
        infoBox.setDetailedText("Detailed Text")
        infoBox.setStandardButtons(QMessageBox.Ok | QMessageBox.Cancel)
        infoBox.setEscapeButton(QMessageBox.Close)       


    def closeEvent(self, event):        
        reply = QMessageBox.question(self, 'Exit', "Are you sure you want to exit?", QMessageBox.Yes | QMessageBox.No, QMessageBox.No)                                      
        if reply == QMessageBox.Yes:
            event.accept()
        else:
            event.ignore()

if __name__ == '__main__':
    app = QApplication(sys.argv)
    screenResolution = app.desktop().screenGeometry()
    screenWidth = screenResolution.width()
    screenHeight = screenResolution.height()
    example = mainWindow(screenWidth, screenHeight)
    sys.exit(app.exec_())

Answer 1

You might need a

infoBox.exec_() 

at the end to actually execute it

Answer 2

Or no need _ (underline), direct exec:

infoBox.exec()

You need to execute the message-box for it to show.