Python中再pyqt的GUI界面中如何用鼠标绘制笔直的直线，并设定线段的颜色为黄色，并在最后输出这条线段的长度

在PyQt中创建GUI并使用鼠标绘制笔直直线，你可以使用`QGraphicsScene`和`QPainterPath`结合`.addLine()`方法。首先，你需要设置`QGraphicsView`展示场景，并创建`QGraphicsScene`实例。然后，可以在用户按下鼠标按钮时开始绘制，在移动鼠标时添加线条，释放鼠标则完成绘制。

以下是一个简单的示例：

import sys
from PyQt5.QtWidgets import QApplication, QGraphicsView, QMainWindow
from PyQt5.QtGui import QPainter, QColor, QPainterPath

class GraphicsWindow(QMainWindow):
    def __init__(self):
        super(GraphicsWindow, self).__init__()
        
        self.scene = QGraphicsScene()
        self.view = QGraphicsView(self.scene)
        self.path = QPainterPath()

        self.setCentralWidget(self.view)

        self.start_point = None
        self.end_point = None
        self.line_color = QColor(0xFF, 0xFF, 0x00)  # 黄色

        self.view.mousePressEvent = self.on_mouse_press
        self.view.mouseMoveEvent = self.on_mouse_move
        self.view.mouseReleaseEvent = self.on_mouse_release

    def on_mouse_press(self, event):
        self.start_point = event.pos()
        self.path.moveTo(self.start_point)
    
    def on_mouse_move(self, event):
        if not self.start_point:
            return
        self.path.lineTo(event.pos())
        self.update_line()

    def on_mouse_release(self, event):
        self.end_point = event.pos()
        if self.start_point and self.end_point:
            line_length = self.get_line_length(self.start_point, self.end_point)
            print(f"绘制的黄线长度为: {line_length}px")
            self.path.lineTo(self.end_point)
            self.update_line()
        self.start_point = None

    def update_line(self):
        painter = QPainter(self.scene)
        painter.setPen(QColor(*self.line_color.getRgb()))
        painter.drawPath(self.path)

    @staticmethod
    def get_line_length(start, end):
        return ((end.x() - start.x())**2 + (end.y() - start.y())**2)**0.5

if __name__ == "__main__":
    app = QApplication(sys.argv)
    window = GraphicsWindow()
    window.show()
    sys.exit(app.exec_())

在这个例子中，当鼠标按下、移动和释放时，程序会动态更新路径并在画布上显示黄色直线。`get_line_length`函数计算了两点之间的距离作为线段长度。