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 sys
from 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)
        pass


if __name__ == '__main__':
    app = QApplication(sys.argv)
    win = Mwindow()
    win.setMouseTracking(True)
    win.show()
    sys.exit(app.exec_())