python的dict()字典数据类型的方法详解以及案例使用

1、以前的回顾

# int  数字
# str 字符串
# list 列表
# tuple 元组
# dict 字典

字典中最重要的方法

keys()

values()

items()

get

update

字典是以  "key":"value"  的方式存储的

一、字典里面是键值对，每一个元素之间也是用逗号分隔，是用{}大括号括起来的

字典里面的value能够是任何值，能够无限嵌套列表和元组

布尔值(不能跟0或1一块儿出现，当key里面没有0和1就能够作key)、列表、字典不能做为字典的key

字典是无序的，每次运行，输出的结果都不是固定的

 

2、下面了解下字典的经常使用操做

info = {"k1": "v1", "k2": "v2" } print (info) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'k1': 'v1', 'k2': 'v2'} info = { "k1": 18, "k2": True, "k3":[ 11, [], (), 22, 33, { "kk1":"vv1", "kk2":"vv2", "kk3":(11,22,), } ], "k4":(11,22,33,44,) } print (info) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'k2': True, 'k1': 18, 'k3': [11, 22, 33, {'kk3': (11, 22), 'kk2': 'vv2', 'kk1': 'vv1'}], 'k4': ()}

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2.数字、字符串、布尔值、元组、均可以作key

info = { 2:"abc", "k1":"def", True:"123", (11,22):"456" } print (info) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'k1': 'def', True: '123', 2: 'abc', (11, 22): '456'}

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3.列表和字典都不能做为字典的key

    （1）列表不能做为字典的key

info = { 2:"abc", "k1":"def", True:"123", [11,22]:"456" } TypeError: unhashable type: 'list'

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    （2）字典不能做为字典的key

info = { 2:"abc", "k1":"def", True:"123", {"k3":"v3"}:"456" } TypeError: unhashable type: 'dict'

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四、字典去保存的时候是按照哈希表保存的

五、字典是无序的（发现每次打印结果都不同，因此字典是无序的）

第一次打印

C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py

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

第二次打印

C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py

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

 

6.按照key去取值，好比要取到18这个值应该怎么作（这里就不是索引的的0123这些了）

info = { "k1": 18, "k2": True, "k3":[ 11, [], (), 22, 33, { "kk1":"vv1", "kk2":"vv2", "kk3":(11,22,), } ], "k4":(11,22,33,44,) } v = info["k1"] print (v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py 18

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好比想要拿到99999这个值，就是下面这样写了（由于想拿3这个key对应的value，因此直接就写3这个数字就能够了，不用带双引号）

info = { "k1": 18, 3: 99999, "k3": [ 11, [], (), 22, 33, { "kk1": "vv1", "kk2": "vv2", "kk3": (11, 22,), } ], "k4": (11, 22, 33, 44,) } v = info[3] print(v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py 99999

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七、拿到11 这个元素该怎么写

第一步拿到k3这个key，结果就是一个列表了，想要拿到元组里面的那个11，就得先拿列表里面的整个字典的元素，位置是5

v = info["k3"] print (v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py [11, [], (), 22, 33, {'kk3': (11, 22), 'kk2': 'vv2', 'kk1': 'vv1'}]

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拿到列表里面的这个字典以后，要想取到元组里面的11，首先得拿到kk3这个key对应的value

v = info["k3"][5] print (v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'kk2': 'vv2', 'kk3': (11, 22), 'kk1': 'vv1'}

如今拿到这个元组了，想要元组里面的11这个元素就简单了，11位于这个元素的第0个位置

v = info["k3"][5]["kk3"] print (v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py (11, 22)

拿到元组中的11的这个元素了

v = info["k3"][5]["kk3"][0] print (v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py 11

 

合起来就是下面这

 

info = { "k1": 18, 3: 99999, "k3": [ 11, [], (), 22, 33, { "kk1": "vv1", "kk2": "vv2", "kk3": (11, 22,), } ], "k4": (11, 22, 33, 44,) } v = info["k3"][5]["kk3"][0] print(v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py 11

8.删除字典中的key

info = { "k1": 18, 3: 99999, "k3": [ 11, [], (), 22, 33, { "kk1": "vv1", "kk2": "vv2", "kk3": (11, 22,), } ], "k4": (11, 22, 33, 44,) } del info["k1"] print (info) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {3: 99999, 'k3': [11, [], (), 22, 33, {'kk1': 'vv1', 'kk2': 'vv2', 'kk3': (11, 22)}], 'k4': (11, 22, 33, 44)}

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9.删除kk1这个key

info = { "k1": 18, 3: 99999, "k3": [ 11, [], (), 22, 33, { "kk1": "vv1", "kk2": "vv2", "kk3": (11, 22,), } ], "k4": (11, 22, 33, 44,) } del info["k3"][5]["kk1"] print (info) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'k1': 18, 'k3': [11, [], (), 22, 33, {'kk3': (11, 22), 'kk2': 'vv2'}], 3: 99999, 'k4': (11, 22, 33, 44)}

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十、字典支持for循环，默认循环的时候只有key

info = { "k1": 18, 3: 99999, "k3": [ 11, [], (), 22, 33, { "kk1": "vv1", "kk2": "vv2", "kk3": (11, 22,), } ], "k4": (11, 22, 33, 44,) } for n in info: print (n) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py k1 3 k3 k4

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11.取字典里面的key，字典里面也有一个方法叫keys

info = { "k1": 18, 3: 99999, "k3": [ 11, [], (), 22, 33, { "kk1": "vv1", "kk2": "vv2", "kk3": (11, 22,), } ], "k4": (11, 22, 33, 44,) } # for n in info: # print (n)
v = info.keys() print (v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py dict_keys(['k1', 3, 'k4', 'k3'])

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12.取字典里面的values   有一个方法叫作value，能够结合一下for循环，一个一个的打印出来，为啥只有四行呢，由于key只有4个，这是对应的4个key的4个value

info = { "k1": 18, 3: 99999, "k3": [ 11, [], (), 22, 33, { "kk1": "vv1", "kk2": "vv2", "kk3": (11, 22,), } ], "k4": (11, 22, 33, 44,) } for n in info.values(): print (n) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py 99999 [11, [], (), 22, 33, {'kk3': (11, 22), 'kk2': 'vv2', 'kk1': 'vv1'}] (11, 22, 33, 44) 18

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13.既想拿到key 又想拿到value（本身写for循环）

info = { "k1": 18, 3: 99999, "k3": [ 11, [], (), 22, 33, { "kk1": "vv1", "kk2": "vv2", "kk3": (11, 22,), } ], "k4": (11, 22, 33, 44,) } for n in info.keys(): print (n,info[n]) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py k4 (11, 22, 33, 44) k3 [11, [], (), 22, 33, {'kk2': 'vv2', 'kk3': (11, 22), 'kk1': 'vv1'}] 3 99999 k1 18

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1四、既拿到key又拿到value，字典有一个方法，items  咱们用一下试试

由于是2个值，因此循环的时候，要用两个变量，这样items这个方法才会把key的值赋值给k，把value的值赋值给v，最后在打印k,v

info = { "k1": 18, 3: 99999, "k3": [ 11, [], (), 22, 33, { "kk1": "vv1", "kk2": "vv2", "kk3": (11, 22,), } ], "k4": (11, 22, 33, 44,) } for k,v in info.items(): print (k,v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py k1 18 k4 (11, 22, 33, 44) 3 99999 k3 [11, [], (), 22, 33, {'kk2': 'vv2', 'kk1': 'vv1', 'kk3': (11, 22)}]

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2、dict字典的方法详解

一、clear(self)

D.clear() -> None.  Remove all items from D.

清空字典

 

D = {"11":"aa","22":"bb","33":"cc"} v = D.clear() print (v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py None

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2. copy(self)  浅拷贝

D = {"11":"aa","22":"bb","33":"cc"} v = D.copy() print (v) print (D) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'22': 'bb', '11': 'aa', '33': 'cc'} {'22': 'bb', '11': 'aa', '33': 'cc'}

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3. fromkeys

根据序列，建立字典，并指定统一一个value做为key的值

Returns a new dict with keys from iterable and values equal to value

@staticmethod # known case   这是静态方法的意

def fromkeys(*args, **kwargs）

静态方法是这样使用的  类名.方法

这个必须传2个参数，第一个参数是用来建立字典的key的，必须是可迭代对象，列表、元组，字符串均可以，第二个参数是这些key的统一的值

 

第一个参数是列表的方式

v = dict.fromkeys(["name","11","woai"],123) print (v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'woai': 123, '11': 123, 'name': 123}

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第一个参数是元组的方式

v = dict.fromkeys(("what","66","woai"),123) print (v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'woai': 123, '66': 123, 'what': 123}

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第一个参数是字符串的方式

v = dict.fromkeys("name",123) print (v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'m': 123, 'e': 123, 'n': 123, 'a': 123}

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4. get(self, k, d=None) 

获取key的值

D.get(k[,d]) -> D[k] if k in D, else d.  d defaults to None.

 

咱们经过这种方法的话，若是key不存在的话，程序就直接报错了

D = {"11":"aa","22":"bb","33":"cc"}
v = D["111"]
print (v)

KeyError: '111'

 

get这个方法在取值的时候，直接加key的名字就能够取到key的对应的值

 

D = { "k1":"v1", "k2":"v2" } v = D.get("k1") print(v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py v1

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当要取的这个key不存在时，能够指定一个返回值，默认是None

D = { "k1":"v1", "k2":"v2" } v = D.get("k3") print(v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py None

当要取的这个key不存在时，指定一个固定的返回值

D = { "k1":"v1", "k2":"v2" } v = D.get("k3","000") print(v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py 000

5. items(self)

同时拿到key和value

D = { "k1":"v1", "k2":"v2" } for n in D.items(): print(n) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py ('k2', 'v2') ('k1', 'v1')

6. keys(self)

取出字典中的全部key

D = { "k1":"v1", "k2":"v2" } for n in D.keys(): print(n) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py k2 k1

7. values(self）

取出字典里面的全部value

D = { "k1":"v1", "k2":"v2" } for n in D.values(): print(n) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py v2 v1

8. pop(self, k, d=None)

删除指定的key

D = { "k1":"v1", "k2":"v2" } v = D.pop("k1") print (D) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'k2': 'v2'}

 

删除指定的key并把删除的value打印出来

 

D = { "k1":"v1", "k2":"v2" } v = D.pop("k1") v就是指定删除的key 值是v1 print (D,v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'k2': 'v2'} v1

当删除的指定的key不存在的时候，能够指定一个参数，让结果返回这个指定的参数

D = { "k1":"v1", "k2":"v2" } v = D.pop("k3","000") print (D) print (v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'k1': 'v1', 'k2': 'v2'} 000

9.popitem(self)

随机删除一个key

被删除的key和value是以一个元组的方式输出的 

D = { "k1":"v1", "k2":"v2" } v = D.popitem() print (D) print (v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'k2': 'v2'} ('k1', 'v1')

也能够这样写

D = { "k1":"v1", "k2":"v2" } k,v = D.popitem() print (D,k,v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'k2': 'v2'} k1 v1

10. setdefault(self, k, d=None)

设置key对应的值，

若是参数里面的key已存在，则不设置，获取当前key对应的值

若是参数里面的key不存在，则设置key的值，获取当前key对应的值

 

当key存在的时候，则不设置，而且获取当前key的值

D = { "k1":"v1", "k2":"v2" } v = D.setdefault("k1","woaini") print (D) print (v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'k2': 'v2', 'k1': 'v1'} v1

 

当key不存在的时候，则增长一个key，并设置key的值，并返回参数中指定key的值

D = { "k1":"v1", "k2":"v2" } v = D.setdefault("k3","woaini") print (D) print (v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'k3': 'woaini', 'k2': 'v2', 'k1': 'v1'} woaini

11. update(self, E=None, **F)

若是key存在的话，就更新key的值，若是key不存在的话，就增长到字典里面

k1是在原来基础上修改的，k3是新增的

 

D = { "k1":"v1", "k2":"v2" } D.update({"k1":"333","k3":"666"}) print (D) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'k3': '666', 'k2': 'v2', 'k1': '333'}

第二种写法：

 

D = { "k1":"v1", "k2":"v2" } D.update(k1=111,k3=666,k5="woaini") print (D) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py {'k2': 'v2', 'k5': 'woaini', 'k1': 111, 'k3': 666}

 

D.update(k1=111,k3=666,k5="woaini")

 

至关于在内部自动转换成一个字典，作个更新

若是参数里面是**kwargs  这样的，默认就会把

D.update(k1=111,k3=666,k5="woaini") 自动转换成字典

12.字典里面的in操做

（1）判断字典的key里面是否包含k1

只能判断key不能判断vlaue，想判断value怎么办呢，看（2）

D = { "k1":"v1", "k2":"v2" } v = "k1" in D print (v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py True

 

（2）判断字典里面的value是否包含v1

D = { "k1":"v1", "k2":"v2" } v = "v1" in D.values() print (v) C:\python35\python3.exe D:/pyproject/day12列表/dict-way.py True