Python返回没有从for循环中转义

Question

以下是我解决此问题的代码：

def nfsmaccepts(current, edges, accepting, visited):
    print ('iteration', current, ''.join([i[1] for i in visited]))
    if current in accepting:
        print ('accepted')
        return ''.join([i[1] for i in visited])
    else:
        for edge in edges:
            if edge not in visited and current == edge[0]:
                print (edge, ' matched')
                visited.append(edge)
                for i in edges[edge]:
                    if nfsmaccepts(i, edges, accepting, visited) is not None:
                        print (edge, i, ' chosen')
                        return nfsmaccepts(i, edges, accepting, visited)
                    else:
                        visited = visited[:-1]

结果如下：

^{pr2}$

我不明白为什么当递归函数的一个终端调用已经到达时，程序为什么继续运行for循环而返回None。请帮忙！在

Answer 1

从if语句调用函数时，将出现“accepted”状态：

if nfsmaccepts(i, edges, accepting, visited) is not None

然后继续打印(4, 'c') 5 chosen。上一次迭代也是这样，所以您从迭代4再次调用它，并打印(3, 'b') 4 chosen。在

也许在测试之前只调用一次结果存储？在

^{pr2}$