python字典的基本操作

字典的基本方法

什么是字典:

字典是一种 key - value的数据类型,听alex说就像我们上学用的字典,通过笔划,字母来查找对饮页面的详细内容。

语法:

id_dict = {
    'stu1101': "TengLan Wu",
    'stu1102': "LongZe Luola",
    'stu1103': "XiaoZe Maliya",
}

 

字典的特性:

  dict是无序的

  key必须是唯一的,value可以重复,    key=键,value=值

 

增加:

id_dict["stu1104"] = "smelond"
print(id_dict)
{'stu1101': 'TengLan Wu', 'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya', 'stu1104': 'smelond'}

 

修改:

id_dict["stu1101"] = "amanda"
print(id_dict)
{'stu1101': 'amanda', 'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya'}

 

删除里面的某一项:

print(id_dict)
{'stu1101': 'TengLan Wu', 'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya'}

id_dict.pop(
"stu1101")#标准删除
print(id_dict)
{
'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya'}

 

del删除:

print(id_dict)
{'stu1101': 'TengLan Wu', 'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya'}

del id_dict["stu1101"]#del删除 
print(id_dict)
{'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya'}

 

随机删除:

print(id_dict)
{'stu1101': 'TengLan Wu', 'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya'}

id_dict.popitem()#随机删除
print(id_dict)
{'stu1101': 'TengLan Wu', 'stu1102': 'LongZe Luola'}

 

直接删字典:

print(id_dict)
id_dict.clear() #删除字典里面的所有内容
print(id_dict)

{'stu1101': 'TengLan Wu', 'stu1102': 'LongZe Luola', 'stu1103': 'XiaoZe Maliya'}
{}

 

查找:

print("stu1101" in id_dict)#in查看有没有这个对象
True    #如果有返回真,没有则fFalse

 

获取:

print(id_dict.get("stu1101"))#用get获取如果存在返回key值,不存在则返回None,
TengLan Wu
print(id_dict["stu1101"])#这个方法不会像上面那样智能,key不存在就直接报错 TengLan Wu print(id_dict["stu11231"]) print(id_dict["stu11231"]) KeyError: 'stu11231'

 

多字典嵌套:

#!/usr/bin/env python
# _*_ coding:utf-8 _*_
# File_type:多字典嵌套
# Filename:dict_nest.py
# Author:smelond
id_dict = {
    "ChengDu": {
        "acreage": 14312, "population": "1591.8w", "postalcode": 610000},
    "ShenZhen": {
        "acreage": 1196, "population": "1190.08w", "postalcode": 518000},
    "BeiJing": {
        "acreage": "1.641w", "population": "2172.9w", "postalcode": 100000}
}

print(id_dict["ChengDu"])#打印输出所有的值
print(id_dict["ChengDu"]["acreage"]) #打印输出成都的面积
id_dict[
"ChengDu"]["acreage"] = "面 积:14312平方千米" #给成都的面积重新修改为了"面 积:14312平方千米"
print(id_dict["ChengDu"]["acreage"])#打印

{
'acreage': 14312, 'population': '1591.8w', 'postalcode': 610000}
14312
面 积:14312平方千米

 

将字典转换为元组:

print(id_dict.items())
dict_items([('stu1101', 'TengLan Wu'), ('stu1102', 'LongZe Luola'), ('stu1103', 'XiaoZe Maliya')])

 

将字典转换为列表:

list_test = list(id_dict)
print(list_test)

['stu1101', 'stu1102', 'stu1103']

 

字典的循环:

for key in id_dict:
    print(key, id_dict[key])#由于加入了key,所以他把stu也循环出来了
输出:
stu1101 TengLan Wu
stu1102 LongZe Luola
stu1103 XiaoZe Maliya

for key in id_dict:
    print(id_dict[key])
输出:
TengLan Wu
LongZe Luola
XiaoZe Maliya

 

多字典嵌套的循环:

#!/usr/bin/env python
# _*_ coding:utf-8 _*_
# File_type:多字典嵌套
# Filename:dict_nest.py
# Author:smelond
id_dict = {
    "ChengDu": {
        "acreage": 14312, "population": "1591.8w", "postalcode": 610000},
    "ShenZhen": {
        "acreage": 1196, "population": "1190.08w", "postalcode": 518000},
    "BeiJing": {
        "acreage": "1.641w", "population": "2172.9w", "postalcode": 100000}
}

for key in id_dict:#还是照常循环
    test = id_dict[key]#将我们每次的key赋给test
    for key in test:#再来循环test
        # print(key, ":", test[key], "\n", end="")
        print("%s : %s" % (key, test[key]))#将第二级的key打印,并且打印出value

acreage : 14312
population : 1591.8w
postalcode : 610000
acreage : 1196
population : 1190.08w
postalcode : 518000
acreage : 1.641w
population : 2172.9w
postalcode : 100000

 

posted @ 2017-11-19 18:24 smelond 阅读(...) 评论(...) 编辑 收藏