PyQt5 Signal and slots(信号和槽)

The sender is an object that sends a signal. The receiver is the object that receives the signal. The slot is the method that reacts to the signal.
event target 发送一个信号，信号接收器接收信号，槽专门用来处理这个信号。

代码：

# coding='utf-8'


from PyQt5.QtWidgets import QWidget, QLCDNumber,\
    QSlider, QVBoxLayout, QApplication
from PyQt5.QtCore import Qt
import sys


class Gui(QWidget):
    def __init__(self):
        super(Gui, self).__init__()
        self.start()

    def start(self):
        # 创建QWidget上的计数器
        lcd = QLCDNumber(self)
        # 创建水平放置在QWidget上的滑条
        sld = QSlider(Qt.Horizontal, self)

        # 创建垂直方向的布局控件
        vbox = QVBoxLayout()
        # 给这个垂直方向的布局控件添加两个子组件
        vbox.addWidget(lcd)
        vbox.addWidget(sld)

        # 设置QWidget窗体的布局为垂直方向布局vbox
        self.setLayout(vbox)

        # 将sld滑条的数值改变与lcd数字显示联系在一起
        # 其中, sld是event source, valueChanged是event target,
        # lcd.display是slot, QWidget是event object
        sld.valueChanged.connect(lcd.display)

        self.setGeometry(300, 300, 250, 150)
        self.setWindowTitle('Signal and slot')
        self.show()


win = QApplication(sys.argv)
gui = Gui()
sys.exit(win.exec_())