点击按钮退出窗口

如图所示，当点击quit按钮时，退出窗口

代码：

"""
This program creates a quit
button. When we press the button,
the application terminates.
"""

import sys
from PyQt5.QtWidgets import QWidget, QPushButton, QApplication


class Example(QWidget):

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

        self.initUI()

    def initUI(self):

        # create a push button
        quitbtn = QPushButton('Quit', self)
        # QPushButton(string text, QWidget parent = None)
        # The text parameter is a text that will be displayed on the button
        # The parent is a widget on which we place our button

        quitbtn.clicked.connect(QApplication.instance().quit)
        # The clicked signal is connected to the quit() method which terminates the application.
        # The communication is done between two objects: the sender and the receiver.
        # The sender is the push button, the receiver is the application object.

        quitbtn.resize(quitbtn.sizeHint())
        quitbtn.move(50, 50)

        self.setGeometry(300, 300, 250, 150)
        self.setWindowTitle('Quit button')
        self.show()


if __name__ == '__main__':

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