为部件提供浮动提示信息

效果如下（由于不方便截图，就另存了教程中的图片）：

                               （加上提示信息即为实际截图）

"""
This example shows a tooltip on
a window and a button.
"""
import sys
from PyQt5.QtWidgets import (QWidget, QToolTip, QPushButton, QApplication)
from PyQt5.QtGui import QFont


class Example(QWidget):

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

    def initUI(self):

        # We use a 10px SansSerif font.
        QToolTip.setFont(QFont('SansSerif', 10))
        # This static method sets a font used to render tooltips.

        # To create a tooltip, we call the setTooltip() method.
        self.setToolTip('This is a <b>QWidget</b> widget')

        # create a push button widget and set a tooltip for it
        btn = QPushButton('Button', self)
        btn.setToolTip('This is a <b>QPushButton</b> widget')
        btn.resize(btn.sizeHint())
        # The sizeHint() method gives a recommended size for the button
        
        btn.move(50, 50)

        self.setGeometry(300, 300, 300, 200)
        self.setWindowTitle('Tooltips')
        self.show()


if __name__ == '__main__':

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