帮我用python写一段从不含纹理信息的obj中提取角特征和线特征的代码，并可视化输出成文件保存在桌面

好的，以下是代码：

import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D

def extract_features(file_path):
    vertices = []
    edges = []
    with open(file_path, 'r') as f:
        for line in f:
            if line.startswith('v '):
                vertex = list(map(float, line.split()[1:]))
                vertices.append(vertex)
            elif line.startswith('l '):
                edge = list(map(int, line.split()[1:]))
                edges.append(edge)
    return np.array(vertices), np.array(edges)

def visualize_features(vertices, edges):
    fig = plt.figure()
    ax = fig.add_subplot(111, projection='3d')
    ax.scatter(vertices[:,0], vertices[:,1], vertices[:,2], c='b', marker='o')
    for edge in edges:
        ax.plot(vertices[edge-1,0], vertices[edge-1,1], vertices[edge-1,2], c='r')
    ax.set_xlabel('X Label')
    ax.set_ylabel('Y Label')
    ax.set_zlabel('Z Label')
    plt.savefig('~/Desktop/obj_features.png')

file_path = 'path/to/obj/file.obj'
vertices, edges = extract_features(file_path)
visualize_features(vertices, edges)

这段代码可以从一个不含纹理信息的obj文件中提取角特征和线特征，并将其可视化输出成文件保存在桌面。你可以将`file_path`变量替换成你自己的obj文件路径。