python的dict()字典數據類型的方法詳解以及案例使用

1、以前的回顧

# int  數字
# str 字符串
# list 列表
# tuple 元組
# dict 字典

字典中最重要的方法

keys()

values()

items()

get

update

字典是以  "key":"value"  的方式存儲的

一、字典裏面是鍵值對，每一個元素之間也是用逗號分隔，是用{}大括號括起來的

字典裏面的value能夠是任何值，能夠無限嵌套列表和元組

布爾值(不能跟0或1一塊兒出現，當key裏面沒有0和1就能夠作key)、列表、字典不能做爲字典的key

字典是無序的，每次運行，輸出的結果都不是固定的

 

2、下面瞭解下字典的經常使用操做

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.數字、字符串、布爾值、元組、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爲字典的key

    （1）列表不能做爲字典的key

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

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    （2）字典不能做爲字典的key

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

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四、字典去保存的時候是按照哈希表保存的

五、字典是無序的（發現每次打印結果都不同，因此字典是無序的）

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這個值應該怎麼作（這裏就不是索引的的0123這些了）

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這個值，就是下面這樣寫了（由於想拿3這個key對應的value，因此直接就寫3這個數字就能夠了，不用帶雙引號）

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 這個元素該怎麼寫

第一步拿到k3這個key，結果就是一個列表了，想要拿到元組裏面的那個11，就得先拿列表裏面的整個字典的元素，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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拿到列表裏面的這個字典以後，要想取到元組裏面的11，首先得拿到kk3這個key對應的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'}

如今拿到這個元組了，想要元組裏面的11這個元素就簡單了，11位於這個元素的第0個位置

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

拿到元組中的11的這個元素了

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

 

合起來就是下面這

 

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.刪除字典中的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.刪除kk1這個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循環，默認循環的時候只有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.取字典裏面的key，字典裏面也有一個方法叫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.取字典裏面的values   有一個方法叫作value，能夠結合一下for循環，一個一個的打印出來，爲啥只有四行呢，由於key只有4個，這是對應的4個key的4個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（本身寫for循環）

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，字典有一個方法，items  咱們用一下試試

由於是2個值，因此循環的時候，要用兩個變量，這樣items這個方法纔會把key的值賦值給k，把value的值賦值給v，最後在打印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字典的方法詳解

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)  淺拷貝

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

根據序列，建立字典，並指定統一一個value做爲key的值

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

@staticmethod # known case   這是靜態方法的意

def fromkeys(*args, **kwargs）

靜態方法是這樣使用的  類名.方法

這個必須傳2個參數，第一個參數是用來建立字典的key的，必須是可迭代對象，列表、元組，字符串均可以，第二個參數是這些key的統一的值

 

第一個參數是列表的方式

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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第一個參數是元組的方式

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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第一個參數是字符串的方式

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) 

獲取key的值

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

 

咱們經過這種方法的話，若是key不存在的話，程序就直接報錯了

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

KeyError: '111'

 

get這個方法在取值的時候，直接加key的名字就能夠取到key的對應的值

 

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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當要取的這個key不存在時，能夠指定一個返回值，默認是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

當要取的這個key不存在時，指定一個固定的返回值

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)

同時拿到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）

取出字典裏面的全部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)

刪除指定的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'}

 

刪除指定的key並把刪除的value打印出來

 

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

當刪除的指定的key不存在的時候，能夠指定一個參數，讓結果返回這個指定的參數

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)

隨機刪除一個key

被刪除的key和value是以一個元組的方式輸出的 

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')

也能夠這樣寫

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)

設置key對應的值，

若是參數裏面的key已存在，則不設置，獲取當前key對應的值

若是參數裏面的key不存在，則設置key的值，獲取當前key對應的值

 

當key存在的時候，則不設置，而且獲取當前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

 

當key不存在的時候，則增長一個key，並設置key的值，並返回參數中指定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存在的話，就更新key的值，若是key不存在的話，就增長到字典裏面

k1是在原來基礎上修改的，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'}

第二種寫法：

 

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")

 

至關於在內部自動轉換成一個字典，作個更新

若是參數裏面是**kwargs  這樣的，默認就會把

D.update(k1=111,k3=666,k5="woaini") 自動轉換成字典

12.字典裏面的in操做

（1）判斷字典的key裏面是否包含k1

只能判斷key不能判斷vlaue，想判斷value怎麼辦呢，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）判斷字典裏面的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