How to create a hierarchical data storage class

[briley]

Got a list. How do you keep this in class?

input= [
    (None, 'a'),
    (None, 'b'),
    (None, 'c'),
    ('a', 'a1'),
    ('a', 'a2'),
    ('a2', 'a21'),
    ('a2', 'a22'),
    ('b', 'b1'),
    ('b1', 'b11'),
    ('b11', 'b111'),
    ('b', 'b2'),
    ('c', 'c1'),
]

It's like a class. I don't know how to get a parent element.

class Node(object):
    def __init__(self):
        self.children = []
def add_child(self, obj):
    self.children.append(obj)

[Avante]

Added the name, parent, introduced a specific knot - the root element

In filling the elements, a dictionary was used to facilitate the search for elements

To test the structure ' s performance, a method was used Node.print and all of its children

class Node:
    def __init__(self, name: str, parent: 'Node' = None):
        self.name = name
        self.parent = parent
        self.children = []
def add_child(self, obj: 'Node'):
    self.children.append(obj)

@property
def parent_name(self) -> str:
    return self.parent.name if self.parent else None

def __repr__(self) -> str:
    return f'Node(name={self.name!r}, parent={self.parent_name!r}, children_len={len(self.children)})'

def print(self):
    def _print(node: Node, level=0):
        print('    ' * level + f'{node.name} ({len(node.children)})')
        for child in node.children:
            _print(child, level + 1)

    _print(self)

source = [

(None, 'a'),

(None, 'b'),

(None, 'c'),

('a', 'a1'),

('a', 'a2'),

('a2', 'a21'),

('a2', 'a22'),

('b', 'b1'),

('b1', 'b11'),

('b11', 'b111'),

('b', 'b2'),

('c', 'c1'),

]
name_by_node = dict()

name_by_node[None] = Node('ROOT', None)
for parent, child in source:

parent_node = name_by_node[parent]

if child not in name_by_node:

name_by_node[child] = Node(child, parent_node)
parent_node.add_child(name_by_node[child])

name_by_node[None].print()

Recurring conclusion:

ROOT (3)

a (2)

a1 (0)

a2 (2)

a21 (0)

a22 (0)

b (2)

b1 (1)

b11 (1)

b111 (0)

b2 (0)

c (1)

c1 (0)

---

UPD.

To generate the dictionary, a method should be added:

    def to_dict(self) -> dict:

def _to_dict(node: Node):

return {

'name': node.name,

'parent': node.parent_name,

'children': [_to_dict(child) for child in node.children],

}

    return _to_dict(self)

Call (for ease in json):

data = name_by_node[None].to_dict()

print(json.dumps(data, indent=4, ensure_ascii=False))

Result:

{

"name": "ROOT",

"parent": null,

"children": [

{

"name": "a",

"parent": "ROOT",

"children": [

{

"name": "a1",

"parent": "a",

"children": []

},

{

"name": "a2",

"parent": "a",

"children": [

{

"name": "a21",

"parent": "a2",

"children": []

},

{

"name": "a22",

"parent": "a2",

"children": []

}

]

}

]

},

{

"name": "b",

"parent": "ROOT",

"children": [

{

"name": "b1",

"parent": "b",

"children": [

{

"name": "b11",

"parent": "b1",

"children": [

{

"name": "b111",

"parent": "b11",

"children": []

}

]

}

]

},

{

"name": "b2",

"parent": "b",

"children": []

}

]

},

{

"name": "c",

"parent": "ROOT",

"children": [

{

"name": "c1",

"parent": "c",

"children": []

}

]

}

]

}