python - Python中的递归循环函数

Question

我有一个数据库，该数据库将文件夹关系建模为 n 嵌套级别。对于任何给定的文件夹，我想生成所有子文件夹的列表。

假设我有一个名为 getChildFolders() 的函数，调用这种递归循环的最有效方法是什么？

以下代码适用于 4 层嵌套，但我希望在指定递归深度或在没有更多子项可跟随时智能地停止循环方面有更大的灵 active 。

folder_ids = []
folder_ids.append(folder.id)
for entry in child_folders:
    folder_ids.append(entry.id)
    child_folders_1 = getChildFolders(entry.id)
    for entry_1 in child_folders_1:
        folder_ids.append(entry_1.id)
        child_folders_2 = getChildFolders(entry_1.id)
        for entry_2 in child_folders_2:
            folder_ids.append(entry_2.id)
            child_folders_3 = getChildFolders(entry_2.id)
            for entry_3 in child_folders_3:
                folder_ids.append(entry_3.id)

Answer 1

递归函数是执行此操作的好方法:

def collect_folders(start, depth=-1)
    """ negative depths means unlimited recursion """
    folder_ids = []

    # recursive function that collects all the ids in `acc`
    def recurse(current, depth):
        folder_ids.append(current.id)
        if depth != 0:
            for folder in getChildFolders(current.id):
                # recursive call for each subfolder
                recurse(folder, depth-1)

    recurse(start, depth) # starts the recursion
    return folder_ids