pyqt5 初始

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


class Example(QWidget):

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

        self.initUI()

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

        self.setToolTip('This is a <b>QWidget</b> widget')

        btn = QPushButton('退出', self)
        btn.setToolTip('This is a <b>QPushButton</b> widget')
        btn.resize(btn.sizeHint())
        btn.move(50, 50)

        btn.clicked.connect(QCoreApplication.instance().quit)

        self.setGeometry(300, 300, 300, 200)
        self.setWindowTitle('Tooltips')
        self.setWindowIcon(QIcon('y7.png'))
        self.center()

        self.show()

    def center(self):

        qr = self.frameGeometry()
        cp = QDesktopWidget().availableGeometry().center()
        qr.moveCenter(cp)
        self.move(qr.topLeft())
    def closeEvent(self, event):

        reply = QMessageBox.question(self, 'Message',
                                     "Are you sure to quit?", QMessageBox.Yes |
                                     QMessageBox.No, QMessageBox.No)

        if reply == QMessageBox.Yes:
            event.accept()
        else:
            event.ignore()


if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())