前戲：

1. 列表添加：

   v1 = [1,2,3,4]
   v1.append(123)
   print(v1)
   
   
   data = [
       [11,22,33],
       [44,55,66]
   ]
   
   data[0].append(data[1])
   print(data)
   # data = [
   #     [11,22,33, [44,55,66]],
   #     [44,55,66]
   # ]
   data[1].append(77)
   print(data)
   # data = [
   #     [11,22,33, [44,55,66,77]],
   #     [
    
   44,55,66,77]
   # ]
   print(data[0][3])
   #[44, 55, 66, 77]

   列表添加元素練習
2. 字典添加：

   v1 = {‘k1‘:‘v1‘}
   v1[‘k2‘] = ‘v2‘
   print(v1)
   
   
   data = [
       {‘k1‘:‘v1‘},
       {‘k2‘:‘v2‘}
   ]
   
   for item in data:
       item[‘kk‘] = ‘vv‘
   
   print(data)

   字典添加元素練習

案例：

　　如果parent_id非0，並且parent_id等於id 就添加到id值相同得那行：

# msg_list = [
#     {‘id‘:1,‘content‘:‘xxx‘,‘parent_id‘:None},
#     {‘id‘:2,‘content‘:‘xxx‘,‘parent_id‘:None},
#     {‘id‘:3,‘content‘:‘xxx‘,‘parent_id‘:None},
#     {‘id‘:4,‘content‘:‘xxx‘,‘parent_id‘:1},
#     {‘id‘:5,‘content‘:‘xxx‘,‘parent_id‘:4},
#     {‘id‘:6,‘content‘:‘xxx‘,‘parent_id‘:2},
#     {‘id‘:7,‘content‘:‘xxx‘,‘parent_id‘:5},
 
#     {‘id‘:8,‘content‘:‘xxx‘,‘parent_id‘:3},
# ]
"""
msg_list = [
      {
         ‘id‘:1,‘content‘:‘xxx‘,parent_id:None,child:[
            {‘id‘:4,‘content‘:‘xxx‘,parent_id:1},
            {‘id‘:5,‘content‘:‘xxx‘,parent_id:1,child:[
               {‘id‘:7,‘content‘:‘xxx‘,parent_id:5},
            ]}]
         },
         {‘id‘:2,‘content‘:‘xxx‘,parent_id:None,child:[
            {‘id‘:6,‘content‘:‘xxx‘,parent_id:2},
         ]},
         {‘id‘:3,‘content‘:‘xxx‘,parent_id:None,child:[
            {‘id‘:8,‘content‘:‘xxx‘,parent_id:3},
         ]},
   ]
"""

案例代碼：

msg_list = [
    {‘id‘:1,‘content‘:‘xxx‘,‘parent_id‘:None},
    {‘id‘:2,‘content‘:‘xxx‘,‘parent_id‘:None},
    {‘id‘:3,‘content‘:‘xxx‘,‘parent_id‘:None},
    {‘id‘:4,‘content‘:‘xxx‘,‘parent_id‘:1},
    {‘id‘:5,‘content‘:‘xxx‘,‘parent_id‘:4},
    {‘id‘:6,‘content‘:‘xxx‘,‘parent_id‘:2},
    {‘id‘:7,‘content‘:‘xxx‘,‘parent_id‘:5},
    {‘id‘:8,‘content‘:‘xxx‘,‘parent_id‘:3},
]

# v = [ row.setdefault(‘child‘,[]) for row in msg_list]
# 列表生成式

msg_list_dict = {
}

for item in msg_list:
    item[‘child‘]=[]
    msg_list_dict[item[‘id‘]] = item

result = []
for item in msg_list:
    pid = item[‘parent_id‘]
    if pid:
        msg_list_dict[pid][‘child‘].append(item)
    else:
        result.append(item)

for i in result:
    print(i)

解題思路：

1. 通過冒泡算法進行解答。【推薦】
2. 通過for嵌套for循環亦可以實現，但是效率較低。

知識擴展：

　　算法練習

報障系統之多級評論前戲