The following script shows how we can center a window on the desktop screen.

#!/usr/bin/python

# -*- coding: utf-8 -*-

"""

ZetCode PyQt4 tutorial 

This program centers a window

on the screen. 

author: Jan Bodnar

website: zetcode.com

last edited: October 2011

"""

import sys

from PyQt4 import QtGui

class Example(QtGui.QWidget):

    def __init__(self):

        super(Example, self).__init__()

        self.initUI()

    def initUI(self):               

        self.resize(250, 150)

        self.center()

        self.setWindowTitle('Center')

        self.show()

    def center(self):

        qr = self.frameGeometry()

        cp = QtGui.QDesktopWidget().availableGeometry().center()

        qr.moveCenter(cp)

        self.move(qr.topLeft())

def main():

    app = QtGui.QApplication(sys.argv)

    ex = Example()

    sys.exit(app.exec_())

if __name__ == '__main__':

    main()

The QtGui.QDesktopWidget class provides information about the user's desktop, including the screen size.

self.center()

The code that will center the window is placed in the custom center() method.

qr = self.frameGeometry()

We get a rectangle specifying the geometry of the main window. This includes any window frame.

cp = QtGui.QDesktopWidget().availableGeometry().center()

We figure out the screen resolution of our monitor. And from this resolution, we get the center point.

qr.moveCenter(cp)

Our rectangle has already its width and height. Now we set the center of the rectangle to the center of the screen. The rectangle's size is unchanged.

self.move(qr.topLeft())

We move the top-left point of the application window to the top-left point of the qr rectangle, thus centering the window on our screen.