如何从有序邻接表构建递归字典树

Question

I've been trying to figure this out all day and Im at my wits end. Maybe I'm just getting to old for this.

I'm trying to build a tree for the load_bulk feature on django-treebeard as specified here

To save you looking, it should look like this:

data = [{'data':{'desc':'1'}},
         {'data':{'desc':'2'}, 'children':[
          {'data':{'desc':'21'}},
          {'data':{'desc':'22'}},
          {'data':{'desc':'23'}, 'children':[
            {'data':{'desc':'231'}},
          ]},
          {'data':{'desc':'24'}},
        ]},
        {'data':{'desc':'3'}},
        {'data':{'desc':'4'}, 'children':[
          {'data':{'desc':'41'}},
        ]},
]

'data' holds the record, and if it has children, 'children' is a list of more 'data' dicts (that can also contain a list of children and so on recursively)

I get the data as an ordered list (ordered as in depth first, not by id):

eg:

[
    {'id': 232, 'name': 'jon', 'parent': 'None'}
    {'id': 3522, 'name': 'dave', 'parent': '232'}
    {'id': 2277, 'name': 'alice', 'parent': '3522'}
    {'id': 119, 'name': 'gary', 'parent': '232'}
    {'id': 888, 'name': 'gunthe', 'parent': '119'}
    {'id': 750, 'name': 'beavis', 'parent': 'None'}
    {'id': 555, 'name': 'urte', 'parent': '750'}
]

How can I transform it into a treebeard compliant dictionary that would look like this (typo's excepted):

[
{'data': {'id': 232, 'name': 'jon', 'parent': 'None'},
 'children': [
              {'data': {'id': 3522, 'name': 'dave', 'parent': '232'},
               'children': [
                            {'data': {'id': 2277, 'name': 'alice', 'parent': '3522'}}
                           ]
              }
              {'data': {'id': 119, 'name': 'gary', 'parent': '232'},
               'children': [
                            {'id': 888, 'name': 'gunthe', 'parent': '119'}
                           ]
              }
             ]
{'data': {'id': 750, 'name': 'beavis', 'parent': 'None'},
 'children': [
              {'id': 555, 'name': 'urte', 'parent': '750'}
             ]
}

]

I guess I need some kind of recursion function seeing as its a recursive structure but all my attempts have failed. My brain doesnt do recursion so good.

I did a lot of searching and found mostly solutions pertaining to lists or other structures that i cant mould to fit. I'm a relative noob. ps i had more fun manually typing out the example than i did the rest of day (apart from dinner time).

Answer 1

Maybe there are better ways, but here is one solution:

users = [
    {
        'id': 232,
        'name': 'jon',
        'parent': None
    },
    {
        'id': 3522,
        'name': 'dave',
        'parent': 232
    },
    {
        'id': 2277,
        'name': 'alice',
        'parent': 3522
    },
    {
        'id': 119,
        'name': 'gary',
        'parent': 232
    },
    {
        'id': 888,
        'name': 'gunthe',
        'parent': 119
    },
    {
        'id': 750,
        'name': 'beavis',
        'parent': None
    },
    {
        'id': 555,
        'name': 'urte',
        'parent': 750
    }
]

users_map = {}
for user in users:
    users_map[user['id']] = user

users_tree = []
for user in users:
    if user['parent'] is None:
        users_tree.append(user)
    else:
        parent = users_map[user['parent']]
        if 'childs' not in parent:
            parent['childs'] = []
        parent['childs'].append(user)

print(users_tree)

#user as {data: user, childs: []}

users_map = {}
for user in users:
    users_map[user['id']] = {'data': user, 'childs': []}

users_tree = []
for user in users:
    if user['parent'] is None:
        users_tree.append(users_map[user['id']])
    else:
        parent = users_map[user['parent']]
        parent['childs'].append(users_map[user['id']])

print(users_tree)