数据类型之字典

字典
帮助用户去表示一个事物的信息（事物是有多个属性）。
info = {"name":'sundy','age':18,'gender':'男','hobby':'同桌'} # 键值
# 请输出：我今天点%s,他的年龄是%s,性别是%s，他喜欢他的%s;
基本格式
data = {键:值,键:值,键:值,键:值,键:值,键:值,}

1. 独有功能

info = {"name":'sundy','age':18,'gender':'男','hobby':'同桌'}
1.keys，获取字典中所有的键。 ['name','age','gender','hobby']

for i in info.keys():
    print(i)

 

D:python3.6python3.6.exe D:/python_code/day01/day05.py
name
age
gender
hobby

2.values，获取字典中所有的值。 ['sundy','18','男','同桌']

info = {"name":'sundy','age':18,'gender':'男','hobby':'同桌'}
for i in info.values():
    print(i)

D:python3.6python3.6.exe D:/python_code/day01/day05.py
sundy
18
男
同桌

3.items，获取字典中的所有键值对

 

info = {"name":'sundy','age':18,'gender':'男','hobby':'同桌'}
for i in info.items():
    print(i)
 
D:python3.6python3.6.exe D:/python_code/day01/day05.py
('name', 'sundy')
('age', 18)
('gender', '男')
('hobby', '同桌')

 

4.get 获取键值，不存在key,则返回None
info = {"k1":"a","name":"sundy","age":1}
print(info["k1"])
#print(info["k1111"]) #没有存在key报错
print(info.get('k1'))
print(info.get('k21',666)) #没有存在key,返回666
print(info.get('k11'))  #没有存在key,返回None,None是python的空

结果：
D:python3.6python3.6.exe D:/python_code/day01/day06.py
a
a
666
None

 

5.pop删除键值对
info = {"k1":"a","name":"sundy","age":1}
result=info.pop("k1")
print(info,result)

结果：
D:python3.6python3.6.exe D:/python_code/day01/day06.py
{'name': 'sundy', 'age': 1} a

 

6.update 不存在键值对则添加，存在则更新

info = {"k1":"a","name":"sundy","age":1}
result=info.update({"k2":"a1","k3":"a2"})
print(info)

结果：
D:python3.6python3.6.exe D:/python_code/day01/day06.py
{'k1': 'a', 'name': 'sundy', 'age': 1, 'k2': 'a1', 'k3': 'a2'}

 

 

2. 公共功能
1.长度len
info = {"name":'sundy','age':18,'gender':'男','hobby':'同桌'}
print(len(info))

D:python3.6python3.6.exe D:/python_code/day01/day05.py
4

 

2.索引
info = {"name":'sundy','age':18,'gender':'男','hobby':'同桌'}
print(info['name'])
print(info['age'])

D:python3.6python3.6.exe D:/python_code/day01/day05.py
sundy
18

 

3.for循环
info = {"name":'sundy','age':18,'gender':'男','hobby':'同桌'}
for item in info.keys():   
print(item)

D:python3.6python3.6.exe D:/python_code/day01/day05.py
name
age
gender
hobby

info = {"name":'sundy','age':18,'gender':'男','hobby':'同桌'}
for item in info.values():   
print(item)

D:python3.6python3.6.exe D:/python_code/day01/day05.py
sundy
18
男
同桌

info = {"name":'sundy','age':18,'gender':'男','hobby':'同桌'}
for k,v in info.items():   
print(k,v)

D:python3.6python3.6.exe D:/python_code/day01/day05.py
name sundy
age 18
gender 男
hobby 同桌

 

 

 

for 循环判断

v = {'k1':'v1','k2':'v2','k3':'v3'}
# 默认按照键判断，即：判断x是否是字典的键。
 if 'x' in v:
    pass
# 请判断：k1 是否在其中？
if 'k1' in v:
    pass #
 请判断：v2 是否在其中？
 # 方式一：循环判断
 flag = '不存在'
 for v in v.values():
    if v == 'v2':
        flag = '存在'
 print(flag)

 

4.修改（存在就修改/不存在就增加）
#修改键值
info = {"name":'sundy','age':18,'gender':'男','hobby':'同桌'}
info["name"]="amy"
print(info)

D:python3.6python3.6.exe D:/python_code/day01/day05.py
{'name': 'amy', 'age': 18, 'gender': '男', 'hobby': '同桌'}

info = {"name":'sundy','age':18,'gender':'男','hobby':'同桌'}
info["addr"]="beijing"
print(info)

D:python3.6python3.6.exe D:/python_code/day01/day05.py
{'name': 'sundy', 'age': 18, 'gender': '男', 'hobby': '同桌', 'addr': 'beijin
#修改键
删除后添加

 

删除（键值对）

info = {"name":'sundy','age':18,'gender':'男','hobby':'同桌'}
del info["name"]
print(info)

D:python3.6python3.6.exe D:/python_code/day01/day05.py
{'age': 18, 'gender': '男', 'hobby': '同桌'}

 

重点
数据类型嵌套：int bool str list tuple dict

list tuple dict可以多层嵌套：

val = (1,['sundy','a',1],{"k1":"a","k2":(2,3,"sundy")})
 
打印出(2,3,"sundy")中3
print(val[2]["k2"][1])

D:python3.6python3.6.exe D:/python_code/day01/day05.py
3

#在k2中第一个元素加入a
val = (1,['sundy','a',1],{"k1":"a","k2":[2,3,"sundy"]})
val[2]["k2"].insert(0,"a")
print(val)

D:python3.6python3.6.exe D:/python_code/day01/day05.py
(1, ['sundy', 'a', 1], {'k1': 'a', 'k2': ['a', 2, 3, 'sundy']}

 

总结：
字典的值可以为int bool str list tuple dict类型
字典的key：列表和字典不能为key，其他类型可以

列表，元组：有序
字典：无序（3.6之后字典有序）