在桌面屏幕上居中窗口

效果如下：

"""
This program centers a window
on the screen.
"""
import sys
from PyQt5.QtWidgets import QWidget, QDesktopWidget, QApplication


class Example(QWidget):

    def __init__(self):
        super().__init__()

        self.initUI()

    def initUI(self):

        self.resize(250, 150)
        self.center()

        self.setWindowTitle('Center')
        self.show()

    def center(self):

        # get a rectangle specifying the geometry of the main window
        qr = self.frameGeometry()

        # figure out the screen resolution of our monitor.
        # And from this resolution, we get the center point
        cp = QDesktopWidget().availableGeometry().center()

        # set the center of the rectangle to the center of the screen
        qr.moveCenter(cp)

        # move the top-left point of the application window
        # to the top-left point of the qr rectangle
        self.move(qr.topLeft())


if __name__ == '__main__':

    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())