PyQt - QMessageBox

QMessageBox is a commonly used modal dialog to display some informational message and optionally ask the user to respond by clicking any one of the standard buttons on it. Each standard button has a predefined caption, a role and returns a predefined hexadecimal number.

Important methods and enumerations associated with QMessageBox class are given in the following table −

QMessageBox does not define predefined icons but rather provides them through the style. The default value is No Icon. Message boxes remain the same for all cases. It is recommended to use the standard icons as suggested in the table or as per the style guidelines for the platform.

In this case, none of the predefined icons is suitable for our message box, we can create a custom icon by setting the icon pixmap property instead of the icon property.

Example 1

In this example, illustrate the predefined icon using QMessageBox class and it's method.

import sys
from PyQt6.QtWidgets import QApplication, QWidget, QPushButton, QMessageBox
def window():
   app = QApplication(sys.argv)
   w = QWidget()

   # Create buttons
   b1 = QPushButton(w)
   b1.setText("Information")
   b1.move(45, 50)

   b2 = QPushButton(w)
   b2.setText("Warning")
   b2.move(150, 50)

   b3 = QPushButton(w)
   b3.setText("Question")
   b3.move(50, 150)

   b4 = QPushButton(w)
   b4.setText("Critical")
   b4.move(150, 150)

   # Connect button signals to functions
   b1.clicked.connect(show_info_messagebox)
   b2.clicked.connect(show_warning_messagebox)
   b3.clicked.connect(show_question_messagebox)
   b4.clicked.connect(show_critical_messagebox)

   # Set window title
   w.setWindowTitle("PyQt MessageBox")

   # Show all widgets
   w.show()

   # Start the app
   sys.exit(app.exec())

def show_info_messagebox():
   msg = QMessageBox()
   msg.setIcon(QMessageBox.Icon.Information)
   msg.setText("Information")
   msg.setWindowTitle("Information MessageBox")
   msg.setStandardButtons(QMessageBox.StandardButton.Ok | QMessageBox.StandardButton.Cancel)
   retval = msg.exec()
def show_warning_messagebox():
   msg = QMessageBox()
   msg.setIcon(QMessageBox.Icon.Warning)
   msg.setText("Warning")
   msg.setWindowTitle("Warning MessageBox")
   msg.setStandardButtons(QMessageBox.StandardButton.Ok | QMessageBox.StandardButton.Cancel)
   retval = msg.exec()
def show_question_messagebox():
   msg = QMessageBox()
   msg.setIcon(QMessageBox.Icon.Question)
   msg.setText("Question")
   msg.setWindowTitle("Question MessageBox")
   msg.setStandardButtons(QMessageBox.StandardButton.Ok | QMessageBox.StandardButton.Cancel)
   retval = msg.exec()
def show_critical_messagebox():
   msg = QMessageBox()
   msg.setIcon(QMessageBox.Icon.Critical)
   msg.setText("Critical")
   msg.setWindowTitle("Critical MessageBox")
   msg.setStandardButtons(QMessageBox.StandardButton.Ok | QMessageBox.StandardButton.Cancel)
   retval = msg.exec()

if __name__ == "__main__":
   window()

Output

On executing the code, we see four on-click buttons to get the specific icons.

Example 2

In the following example, click signal of the button on the top level window, the connected function displays the messagebox dialog.

msg = QMessageBox()
msg.setIcon(QMessageBox.Information)
msg.setText("This is a message box")
msg.setInformativeText("This is additional information")
msg.setWindowTitle("MessageBox demo")
msg.setDetailedText("The details are as follows:")

setStandardButton() function displays desired buttons.

msg.setStandardButtons(QMessageBox.Ok | QMessageBox.Cancel)

buttonClicked() signal is connected to a slot function, which identifies the caption of source of the signal.

msg.buttonClicked.connect(msgbtn)

The complete code for the example is as follows −

import sys
from PyQt6.QtCore import *
from PyQt6.QtGui import *
from PyQt6.QtWidgets import *

def window():
   app = QApplication(sys.argv)
   w = QWidget()
   b = QPushButton(w)
   b.setText("Show message!")
   
   b.move(100,50)
   b.clicked.connect(showdialog)
   w.setWindowTitle("PyQt MessageBox demo")
   w.show()
   sys.exit(app.exec_())

def showdialog():
   msg = QMessageBox()
   msg.setIcon(QMessageBox.Information)
   
   msg.setText("This is a message box")
   msg.setInformativeText("This is additional information")
   msg.setWindowTitle("MessageBox demo")
   msg.setDetailedText("The details are as follows:")
   msg.setStandardButtons(QMessageBox.Ok | QMessageBox.Cancel)
   msg.buttonClicked.connect(msgbtn)

   retval = msg.exec_()

def msgbtn(i):
   print ("Button pressed is:",i.text())

if __name__ == '__main__':
   window()

Output

The above code produces the following output. Message Box pops up when main windows button is clicked −

If you click on Ok or Cancel button on MessageBox, the following output is produced on the console −

Button pressed is: OK
Button pressed is: Cancel