python学习之字典

字典是另一种可变容器模型，且可存储任意类型对象。字典的每个键值(key=>value)对用冒号(:)分割，每个对之间用逗号(,)分割，整个字典包括在花括号({})中 ,字典属于dict类，格式如下所示：

1、基本机构

info = {
    "k1": "v1", # 键值对
    "k2": "v2"  # 键值对
}

 2、字典的value可以是任何值

#!/usr/bin/env python
info = {
    "k1": 18,
    "k2": True,
    "k3": [
        11,
        [],
        (),
        22,
        33,
        {
            'kk1': 'vv1',
            'kk2': 'vv2',
            'kk3': (11,22),
        }
    ],
    "k4": (11,22,33,44)
}
print(info)

结果：

{'k1': 18, 'k2': True, 'k3': [11, [], (), 22, 33, {'kk1': 'vv1', 'kk2': 'vv2', 'kk3': (11, 22)}], 'k4': (11, 22, 33, 44)}

3、列表、字典不能作为字典的key

#!/usr/bin/env python
info ={
    1: 'asdf',
    "k1": 'asdf',
    True: "123",
    # [11,22]: 123
    (11,22): 123,
    # {'k1':'v1'}: 123

}
print(info)

结果：

{1: '123', 'k1': 'asdf', (11, 22): 123}

4、索引方式找到指定元素

#!/usr/bin/env python
info = {
    "k1": 18,
    2: True,
    "k3": [
        11,
        [],
        (),
        22,
        33,
        {
            'kk1': 'vv1',
            'kk2': 'vv2',
            'kk3': (11,22),
        }
    ],
    "k4": (11,22,33,44)
}
v = info['k3'][5]['kk3'][0]
print(v)

结果：

11

5、字典支持 del 删除

#!/usr/bin/env python
info = {
    "k1": 18,
    2: True,
    "k3": [
        11,
        [],
        (),
        22,
        33,
        {
            'kk1': 'vv1',
            'kk2': 'vv2',
            'kk3': (11,22),
        }
    ],
    "k4": (11,22,33,44)
}
del info['k1']

del info['k3'][5]['kk1']
print(info)

结果：

{2: True, 'k3': [11, [], (), 22, 33, {'kk2': 'vv2', 'kk3': (11, 22)}], 'k4': (11, 22, 33, 44)}

6、支持for循环

#!/usr/bin/env python
info = {
    "k1": 18,
    2: True,
    "k3": [
        11,
        [],
        (),
        22,
        33,
        {
            'kk1': 'vv1',
            'kk2': 'vv2',
            'kk3': (11,22),
        }
    ],
    "k4": (11,22,33,44)
}
for item in info:
    print(item)

for item in info.keys():
    print(item)

for item in info.values():
    print(item)

for item in info.keys():
    print(item,info[item])

for k,v in info.items():
    print(k,v)
info ={
    "k1": 'asdf',
    True: "123",
    # [11,22]: 123
    (11,22): 123,
    # {'k1':' v1'}: 123

}
print(info)

结果：

k1
2
k3
k4
k1
2
k3
k4
18
True
[11, [], (), 22, 33, {'kk1': 'vv1', 'kk2': 'vv2', 'kk3': (11, 22)}]
(11, 22, 33, 44)
k1 18
2 True
k3 [11, [], (), 22, 33, {'kk1': 'vv1', 'kk2': 'vv2', 'kk3': (11, 22)}]
k4 (11, 22, 33, 44)
k1 18
2 True
k3 [11, [], (), 22, 33, {'kk1': 'vv1', 'kk2': 'vv2', 'kk3': (11, 22)}]
k4 (11, 22, 33, 44)
{'k1': 'asdf', True: '123', (11, 22): 123}

 7、get方法

根据key去取值，如果没有key则返回None,也可以用来表示当要取的key不存在时，用默认的值返回。

dic ={
    "name":'wang',
    "age":23
}
v = dic.get('name')
v1=dic.get('age1')
v2=dic.get('age1',100)
print(v,v1,v2)

结果：
wang None  100

8、pop方法，删除指定的key

dic ={
    "name":'wang',
    "age":23
}
dic.pop('name')
print(dic)


结果：
{'age': 23}

9、setdefault

如果key已经存在，不设置值，获取当前key对应的值

如果key不存在，设置值，获取当前key对应的值

dic ={
    "name":'wang',
    "age":23
}
v=dic.setdefault('name',"zhang")
print(dic,v)

dic1 ={
    "name":'wang',
    "age":23
}
v1=dic1.setdefault('name1',"zhang")
print(dic1,v1)

结果：
{'name': 'wang', 'age': 23} wang
{'name': 'wang', 'name1': 'zhang', 'age': 23} zhang

10、keys、values方法

dic ={
    "name":'wang',
    "age":23
}
v=dic.keys()
v1=dic.values()
print(v,v1)

结果：
dict_keys(['name', 'age']) dict_values(['wang', 23])