day12 Python字典

类：dict

#字典是无序的

1、前戏

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

2、字典的value可以是任何值

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,key值不能重复。

info ={
    #1: 'asdf',
     "k1": 'asjlkdf',
    #True: "123",#True不能跟1同时作为key，重复的只显示一个因为1=True
    #[11,22]: 123
    (11,22): 123,
    #{'k1':'v1'}: 123

}
print(info)

结果：
{'k1': 'asjlkdf', (11, 22): 123}

4、字典无序

5、索引方式找到指定元素

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

结果：
11

6、字典支持del删除

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)}

7、for循环

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

#for循环健
for item in info。key:
    print(item)

#结果
k1
2
k3
k4

#for循环值
for item in info.values():
    print(item)

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

#for循环键值
for k,v in info.items():
    print(k,v)

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

方法：

1、根据序列，创建字典，并指定统一的值

v = dict.fromkeys(["k1",123,"999"],123)
print(v)

结果：
{'k1': 123, 123: 123, '999': 123}

2、根据Key获取值，key不存在，可以指定默认值None

dic = {
    "k1":"v1"
}

v = dic.get('k1',None)
#根据Key获取值，key不存在时，可以指定默认值（None）
v1 = dic.get("k",None)
print(v)
print(v1)

结果：
v1
None

3、删除并获取值

dic = {
    "k1": 'v1',
    "k2": 'v2'
}
v = dic.pop('k1',None)
v1 = dic.pop('k11',None)
print(dic,v)
print(dic,v1)

结果：
{'k2': 'v2'} v1
{'k2': 'v2'} None

4、设置值

dic = {
    "k1": 'v1',
    "k2": 'v2'
}
v = dic.setdefault('k1111','123')
print(dic,v)

结果：
{'k1': 'v1', 'k2': 'v2', 'k1111': '123'} 123
# 已存在，不设置，获取当前key对应的值
# 不存在，设置，获取当前key对应的值

5、更新

dic = {
    "k1": 'v1',
    "k2": 'v2'
}
dic.update({'k1': '111111','k3': 123})
print(dic)
dic.update(k1=123,k3=345,k5="asdf")
print(dic)


结果：
{'k1': '111111', 'k2': 'v2', 'k3': 123}
{'k1': 123, 'k2': 'v2', 'k3': 345, 'k5': 'asdf'}