one信号连接one槽函数

class HaHa(QWidget):
    def __init__(self):
        super(Demo,self).__init__()
        self.resize(120,120)
        self.label = QLabel("label")
        self.btn = QPushButton('button')
        # 增加完槽函数后增加下列一行代码来连接槽函数
        self.btn.clicked.connect(self.ChangeText)
        
        self.v_layout = QVBoxLayout()
        self.v_layout.addWidget(self.label)
        self.v_layout.addWidget(self.btn)

        self.setLayout(self.v_layout)


    def ChangeText(self):
        self.label.setText("hello, I have changed~")
        print("hahaha")