分类方式1:递归方式

data = [
    {"cat_id": 6, "name": "昌平", "parent_id": 5},
    {"cat_id": 3, "name": "青浦", "parent_id": 1},
    {"cat_id": 2, "name": "张江", "parent_id": 4},
    {"cat_id": 4, "name": "浦东", "parent_id": 1},
    {"cat_id": 5, "name": "北京", "parent_id": 0},
    {"cat_id": 1, "name": "上海", "parent_id": 0},
]
'''
上海
-浦东
--张江
-青浦
北京
-昌平
'''
res = []
def sone(data, level=0, parent_id=0):
    for item in data:
        if item['parent_id'] == parent_id:
            item['level'] = level
            res.append(item)
            sone(data, level + 1, item['cat_id'])
    return res


t = sone(data)
print(t)
for i in t:
    print(i['level'] * '-',i['name'])
    
'''
t= [{'cat_id': 5, 'name': '北京', 'parent_id': 0, 'level': 0}, 
     {'cat_id': 6, 'name': '昌平', 'parent_id': 5, 'level': 1}, 
     {'cat_id': 1, 'name': '上海', 'parent_id': 0, 'level': 0}, 
     {'cat_id': 3, 'name': '青浦', 'parent_id': 1, 'level': 1}, 
     {'cat_id': 4, 'name': '浦东', 'parent_id': 1, 'level': 1}, 
     {'cat_id': 2, 'name': '张江', 'parent_id': 4, 'level': 2}]
'''

分类方式2:树状

data = [
    {"cat_id": 3, "name": "青浦", "parent_id": 1},
    {"cat_id": 2, "name": "张江", "parent_id": 4},
    {"cat_id": 4, "name": "浦东", "parent_id": 1},
    {"cat_id": 5, "name": "北京", "parent_id": 0},
    {"cat_id": 6, "name": "昌平", "parent_id": 5},
    {"cat_id": 1, "name": "上海", "parent_id": 0},
]

'''
tree={
    3:{"cat_id":3,"name":"青浦","parent_id":1},
    2:{"cat_id": 2, "name": "张江", "parent_id": 4},
    4:{"cat_id":4,"name":"浦东","parent_id":1},
    5:{"cat_id":5, "name": "北京", "parent_id": 0},
    6:{"cat_id":6, "name": "昌平", "parent_id": 5},
    1:{"cat_id": 1, "name": "上海", "parent_id": 0},
}
'''

def get_tree(data):
    lists = []
    tree = {}
    for i in data:
        tree[i['cat_id']] = i
    for item in data:
        if item['parent_id'] == 0:
            dict1 = tree[item['cat_id']]
            lists.append(dict1)
        else:
            dict2 = tree[item["parent_id"]]
            if "children" not in dict2:
                dict2['children'] = []
            dict2['children'].append(tree[item['cat_id']])
    return lists

print(get_tree(data))


'''
get_tree(data) = [
    {'cat_id': 5, 'name': '北京', 'parent_id': 0,
     'children': [
         {'cat_id': 6, 'name': '昌平', 'parent_id': 5}
     ]
     },
    {'cat_id': 1, 'name': '上海', 'parent_id': 0,
     'children': [
         {'cat_id': 3, 'name': '青浦', 'parent_id': 1},
         {'cat_id': 4, 'name': '浦东', 'parent_id': 1,
          'children': [
              {'cat_id': 2, 'name': '张江', 'parent_id': 4}
          ]
          }
     ]
     }
]

'''

这样就可以通过循环嵌套的级数显示几级分类。
for item in data1:
    print("一级分类:",item['name'])
    for item1 in item["children"]:
        print("二级分类:",item1.get('name'))

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