Python 列表添加字典问题学习记录

import json


def example1():
    dict2 = {}
    dict2_add = []
    dic_a = []
    for i in range (0,3):
        dict2_add.append (dict2)
    print("数据类型1：",type(dict2_add[0]),type(dict2_add[1]),type(dict2_add[2]))
    print("构造列表1:",dict2_add)

    vuln1_info = ['{"a":"aa","b":"bb","c":"cc"}','{"a":"aa1","b":"bb1","c":"cc1"}','{"a":"aa2","b":"bb2","c":"cc2"}']

    for info in vuln1_info:
        name1 = vuln1_info.index (info)
        #print(info)
        dict1 = json.loads (str(info))
        #print(dict1)
        dict2_add[name1]["A"] = dict1["a"]
        dict2_add[name1]["B"] = dict1["b"]
        dict2_add[name1]["C"] = dict1["c"]
        dic_a.append (dict2_add[name1])
    print("生成结果1：",dict2_add)


def example2():
    dict2 = {}
    dict2_add = []
    dic_a = []
    for i in range (0, 3):
        dict2_add.append (dict(dict2))
    print ("数据类型2：", type (dict2_add[0]), type (dict2_add[1]), type (dict2_add[2]))
    print ("构造列表2:", dict2_add)

    vuln1_info = ['{"a":"aa","b":"bb","c":"cc"}', '{"a":"aa1","b":"bb1","c":"cc1"}', '{"a":"aa2","b":"bb2","c":"cc2"}']

    for info in vuln1_info:
        name1 = vuln1_info.index (info)
        # print(info)
        dict1 = json.loads (str (info))
        # print(dict1)
        dict2_add[name1]["A"] = dict1["a"]
        dict2_add[name1]["B"] = dict1["b"]
        dict2_add[name1]["C"] = dict1["c"]
        dic_a.append (dict2_add[name1])
    print("生成结果2：",dict2_add)

if __name__ == "__main__":
    example1()
    print("----------------------------------------------------------------------------------------")
    example2()

输出结果：

数据类型1：   
构造列表1: [{}, {}, {}]
生成结果1： [{'A': 'aa2', 'B': 'bb2', 'C': 'cc2'}, {'A': 'aa2', 'B': 'bb2', 'C': 'cc2'}, {'A': 'aa2', 'B': 'bb2', 'C': 'cc2'}]
----------------------------------------------------------------------------------------
数据类型2：   
构造列表2: [{}, {}, {}]
生成结果2： [{'A': 'aa', 'B': 'bb', 'C': 'cc'}, {'A': 'aa1', 'B': 'bb1', 'C': 'cc1'}, {'A': 'aa2', 'B': 'bb2', 'C': 'cc2'}]

唯一不同就是dict2_add.append (dict2) 与 dict2_add.append (dict(dict2))。

字典赋值习惯性 append一个常量={}，就是添加常量字典，常量字典地址指针指向常量不变，append 添加重复值常量，没有分配新的存储空间，造成例一存在三个重复值。

正常情况下循环生成的字典需要新的存储地址，存储不同的数据，用dict 可以初始化字典，即产生不同地址指向的字典。

dict() -> new empty dictionary dict(mapping) -> new dictionary initialized from a mapping object’s