图形的打印路径，列表索引必须是整数，而不是 str

Question

一直在尝试打印由以下字典定义的图形的所有路径

graph = {
    "a": [
        {"child": "b", "cost": 5},
        {"child": "e", "cost": 8}
    ],
    "b": [
        {"child": "c", "cost": 7},
        {"child": "f", "cost": 2}
    ],
    "d": [
        {"child": "g", "cost": 3},
    ],
    "e": [
        {"child": "d", "cost": 3},
        {"child": "f", "cost": 6}
    ],
    "f": [
        {"child": "c", "cost": 1},
    ],
    "g": [
        {"child": "h", "cost": 10}
    ],
    "h": [
        {"child": "f", "cost": 4}
    ]
}
def print_all_child_paths(graph, node_name):
    node = graph[node_name]

    if len(node) == 0:
        print("No children under this node")
    else:
        x = 1
        for child_node in node:
            print("Path number " + str(x) + ": ")
            print(node_name + " -> ")

            current_node = child_node

            while current_node["child"] in graph:
                print(current_node["child"] + " -> ")
                current_node = graph[current_node["child"]]

            print("END.")
        x += 1

    print("End of paths")

print_all_child_paths(graph, "a")

当我运行函数 print_all_child_paths 时，我以错误 list indices must be integers, not str.

结束

编译器指向第40行，即while循环定义： while current_node["child"] in graph:

我对错误感到困惑，因为循环的条件是检查键是否在字典中。谁能帮我解决这个问题？

提前致谢。

Answer 1

只要在循环的第一次迭代中执行 current_node = graph[current_node["child"]]，current_node 就会变成一个列表，因为 graph 字典的所有值都是列表。

但是，紧接着您的代码尝试在循环条件下执行 current_node["child"]，但是 current_node 作为一个列表，不能用字符串索引，因此出现错误。

Answer 2

每个 node 是一个字典列表。所以 current_node 是一个列表，只能用整数索引访问。您正在尝试将其作为具有字符串键的字典进行访问。您需要遍历节点列表才能访问每个字典。

for child in current node:
    while child["child"] in graph:

图形的打印路径，列表索引必须是整数，而不是 str

Printing paths of a graph, list indices must be integers, not str

python

graph-theory

python-3.x