如何引用在函数中初始化的列表？ (Python)

Question

我收到的错误是赋值前引用的局部变量 'actions'。我有一种感觉，这是因为我在函数中创建列表，然后尝试在其中引用它。这是我收到错误的具体代码。

if node.state == target:
            actions: []
            cells: []

            while node.parent is not None:
                actions.append(node.action)
                cells.append(node.state)
                node = node.parent

这是我正在编写的代码来源的更多上下文。

def shortest_path(source, target):

    """
    Returns the shortest list of (movie_id, person_id) pairs
    that connect the source to the target.

    If no possible path, returns None.
    """
    # Create a frontier
    frontier = QueueFrontier()

    # Initialise explored set
    explored = set()
    # Create a start Node
    node = Node(state=source, parent=None, action=None)
    # Start with the source as a node (The initial state) and add it to the frontier
    frontier.add(node)
    # Start looping until we get a solution
    while True:
        # Check if Frontier is empty then no solution
        if frontier.empty():
            raise Exception("No path found")
        # Remove node from the frontier
        node = frontier.remove()
        # Check if node contains the goal state
        if node.state == target:
            actions: []
            cells: []

            while node.parent is not None:
                actions.append(node.action)
                cells.append(node.state)
                node = node.parent
            actions.reverse()
            cells.reverse()
            solution = (actions, cells)
            return solution

非常感谢您对此提供的帮助。

Answer 1

使用=赋值

if node.state == target:
    actions = []
    cells = []

    while node.parent is not None:
        actions.append(node.action)
        cells.append(node.state)
        node = node.parent

如何引用在函数中初始化的列表？ (Python)

How can I reference a list initialized in a function? (Python)

python

reference

function

list

variable-assignment