通过对按钮绑定函数来生成信号和槽，即信号是按钮点击时发送的信号, 槽为对应绑定的函数

SignalSlotDemo.py 

"""
信号(Signal) 与槽(Slot)
"""
from PyQt5.QtWidgets import *
import sys

class SigalSlotDemo(QWidget):
    def __init__(self):
        super(SigalSlotDemo, self).__init__()
        self.initUI()

    def onClick(self):
        self.btn.setText("信号已经发出")
        self.btn.setStyleSheet("QPushButton(max-width:200px;min-width:200px)")
    def initUI(self):
        self.setGeometry(300, 300, 500, 400)
        self.setWindowTitle("信号(Signal)与槽(Slot)")
        self.btn = QPushButton("我的按钮", self)
        self.btn.clicked.connect(self.onClick)

if __name__ == "__main__":
    app = QApplication(sys.argv)

    main = SigalSlotDemo()
    main.show()

    sys.exit(app.exec_())