def paintEvent(self, event): super().paintEvent(event) painter = QPainter(self) painter.beginNativePainting() painter.setRenderHint(QPainter.Antialiasing) painter.setRenderHint(QPainter.SmoothPixmapTransform) painter.setPen(QPen(Qt.green, 1, Qt.DotLine)) painter.drawRect(self.rubberband.rect()) painter.setPen(QPen(Qt.green, 1)) x_begin = self.rubberband.x() x_half = self.rubberband.x() + self.rubberband.width() / 2 x_full = self.rubberband.x() + self.rubberband.width() y_begin = self.rubberband.y() y_half = self.rubberband.y() + self.rubberband.height() / 2 y_full = self.rubberband.y() + self.rubberband.height() points = [QPoint(x_half, y_begin), QPoint(x_half, y_full)] painter.drawLines(points) painter.endNativePainting() painter.end()