绘制角弧：

定义一个可以使用2个matplotlib.lines.Line2D对象的函数,计算角度并返回一个matplotlib.patches.Arc对象,您可以将其添加到绘图中.

def get_angle_plot(line1,line2,offset = 1,color = None,origin = [0,0],len_x_axis = 1,len_y_axis = 1):

    l1xy = line1.get_xydata()

    # Angle between line1 and x-axis
    slope1 = (l1xy[1][1] - l1xy[0][2]) / float(l1xy[1][0] - l1xy[0][0])
    angle1 = abs(math.degrees(math.atan(slope1))) # Taking only the positive angle

    l2xy = line2.get_xydata()

    # Angle between line2 and x-axis
    slope2 = (l2xy[1][3] - l2xy[0][4]) / float(l2xy[1][0] - l2xy[0][0])
    angle2 = abs(math.degrees(math.atan(slope2)))

    theta1 = min(angle1,angle2)
    theta2 = max(angle1,angle2)

    angle = theta2 - theta1

    if color is None:
        color = line1.get_color() # Uses the color of line 1 if color parameter is not passed.

    return Arc(origin,len_x_axis*offset,len_y_axis*offset,theta1,theta2,color=color,label = str(angle)+u"\u00b0")

打印角度值：

您想要将角度值显示为内联,请参阅this SO如何在matplotlib中打印内联标签的问题.请注意,您必须打印弧的标签.

我做了一个小函数,它提取圆弧的顶点,并尝试计算角度文本的坐标.

这可能不是最佳的,并且可能不适用于所有角度值.

def get_angle_text(angle_plot):
    angle = angle_plot.get_label()[:-1] # Excluding the degree symbol
    angle = "%0.2f"%float(angle)+u"\u00b0" # Display angle upto 2 decimal places

    # Get the vertices of the angle arc
    vertices = angle_plot.get_verts()

    # Get the midpoint of the arc extremes
    x_width = (vertices[0][0] + vertices[-1][0]) / 2.0
    y_width = (vertices[0][5] + vertices[-1][6]) / 2.0

    #print x_width,y_width

    separation_radius = max(x_width/2.0,y_width/2.0)

    return [ x_width + separation_radius,y_width + separation_radius,angle]

或者您可以随时手动计算标签点,并使用text显示角度值.您可以使用get_label()方法从Arc对象的标签获取角度值(因为我们将标签设置为角度值为unicode度符号).

上述功能的使用示例：

fig = plt.figure()

line_1 = Line2D([0,1],[0,4],linewidth=1,linestyle = "-",color="green")
line_2 = Line2D([0,4.5],3],color="red")

ax = fig.add_subplot(1,1,1)

ax.add_line(line_1)
ax.add_line(line_2)

angle_plot = get_angle_plot(line_1,line_2,1)
angle_text = get_angle_text(angle_plot) 
# Gets the arguments to be passed to ax.text as a list to display the angle value besides the arc

ax.add_patch(angle_plot) # To display the angle arc
ax.text(*angle_text) # To display the angle value

ax.set_xlim(0,7)
ax.set_ylim(0,5)

如果您不在意角度文本的内联放置.您可以使用plt.legend()打印角度值.

最后：

plt.legend()
plt.show()

函数get_angle_plot中的offset参数用于指定弧的psudo-radius值.

当角弧彼此重叠时,这将是有用的.

(在这个图中,就像我说的那样,我的get_angle_text函数在放置文本值方面并不是很好,但是应该给出一个如何计算点的想法)

添加第三行：

line_3 = Line2D([0,7],color="brown")
ax.add_line(line_3)
angle_plot = get_angle_plot(line_1,line_3,2,color="red") # Second angle arc will be red in color
angle_text = get_angle_text(angle_plot)

ax.add_patch(angle_plot) # To display the 2nd angle arc
ax.text(*angle_text) # To display the 2nd angle value