'Ant' object has no attribute 'id'

非常抱歉，我之前的代码里有一个错误。在 `Ant` 类中没有定义 `id` 属性，所以调用 `ant.id` 时会出现 `'Ant' object has no attribute 'id'` 的错误。下面是修改后的代码，已经添加了 `id` 属性：

import random
import numpy as np

# 非对称TSP问题的距离矩阵
distances = np.array([[0, 3, 4, 2],
                      [2, 0, 5, 6],
                      [4, 5, 0, 7],
                      [3, 2, 6, 0]])

# 蚂蚁数量
num_ants = 5

# 信息素初始值
pheromone = np.ones(distances.shape) / len(distances)

# 信息素挥发率
evaporation_rate = 0.5

# 信息素增强强度
alpha = 1

# 启发式信息强度
beta = 1

# 最大迭代次数
max_iterations = 100

# 记录每只蚂蚁走过的路径长度
ant_distances = np.zeros(num_ants)

# 记录最短路径长度和路径
best_distance = float('inf')
best_path = []

# 蚂蚁类
class Ant:
    def __init__(self, start_city, id):
        self.path = [start_city]
        self.visited = set([start_city])
        self.id = id

    def choose_next_city(self):
        current_city = self.path[-1]
        unvisited_cities = set(range(len(distances))) - self.visited
        if not unvisited_cities:
            return None
        probabilities = [pheromone[current_city][next_city]**alpha *
                         (1.0/distances[current_city][next_city])**beta
                         for next_city in unvisited_cities]
        probabilities = np.array(probabilities) / sum(probabilities)
        next_city = np.random.choice(list(unvisited_cities), p=probabilities)
        self.path.append(next_city)
        self.visited.add(next_city)
        return next_city

    def update_pheromone(self):
        for i in range(len(self.path)-1):
            current_city, next_city = self.path[i], self.path[i+1]
            pheromone[current_city][next_city] += 1.0 / ant_distances[self.id]

# 初始化蚂蚁
ants = [Ant(random.randint(0, len(distances)-1), i) for i in range(num_ants)]

# 迭代
for iteration in range(max_iterations):
    # 蚂蚁走路
    for ant in ants:
        while ant.choose_next_city() is not None:
            pass
        ant_distances[ant.id] = sum(distances[ant.path[i]][ant.path[i+1]] for i in range(len(ant.path)-1))
        if ant_distances[ant.id] < best_distance:
            best_distance = ant_distances[ant.id]
            best_path = ant.path

    # 更新信息素
    pheromone *= evaporation_rate
    for ant in ants:
        ant.update_pheromone()

    # 重置蚂蚁
    ants = [Ant(random.randint(0, len(distances)-1), i) for i in range(num_ants)]

print('最短路径长度：', best_distance)
print('最短路径：', best_path)

在修改后的代码中，我添加了一个 `id` 参数，用于给每个蚂蚁分配一个唯一的标识符。这样，在更新信息素时，就可以根据每只蚂蚁的 `id` 属性来找到对应的路径长度，从而避免了之前的错误。