鼠标移动事件崩溃的解决方法：为什么我的mouseMoveEvent方法会崩溃？

import sysfrom PyQt5.Qt import *class Mwindow(QWidget):    def __init__(self):        super().__init__()        self.resize(500, 500)        self.move(250, 150)        self.setup_Ui()    def setup_Ui(self):        self.btn = QPushButton(self)        self.btn.setText("点击我")        self.btn.move(230, 150)    def mousePressEvent(self, evt):        self.mousex = evt.globalX()        self.mousey = evt.globalY()        self.btn_x = self.btn.x()        self.btn_y = self.btn.y()    def mouseMoveEvent(self, evt2):        # 检查 mousex 和 mousey 是否已赋值        if hasattr(self, "mousex") and hasattr(self, "mousey"):            print(self.mousex, self.mousey)    def mouseReleaseEvent(self, evt3):        # print(self.mouse_x,self.mouse_y)        passif __name__ == '__main__':    app = QApplication(sys.argv)    win = Mwindow()    win.setMouseTracking(True)    win.show()    sys.exit(app.exec_())