字典:python中非常重要的數據類型,在python中唯一一個映射的數據類型
數據類型分類

按照數據可變與不可變:
 # 不可變數據類型: int str bool tuple
 # 可變數據類型: list,dict,set

1  鍵值對
#字典的   key:value# key 是唯一的 且是不可變數據類型  int,str bool tuple

#value:任意數據類型 

2 . 增加數據

dic = {"name":"jin","age":18,"sex":"male"}
#增 dic[‘key‘] = value
# 有key 就覆蓋,沒有key就添加.
# dic[‘name2‘] = ‘依米‘   #沒有key name2 就會添加新數據
 

# print(dic)
# dic[‘name‘] = ‘王子‘   #有key name  那麽name的值就會被替代
# print(dic)

結果:

.setdefault 方法有key不變, 沒有key才添加.

dic = {"name":"jin","age":18,"sex":"male"}
#有key不變,沒有key才添加.

# dic.setdefault(‘hobby‘)  #沒有會添加

# print(dic)

# dic.setdefault(‘hobby‘,‘開船‘)#有就不會變

# print(dic)
# dic.setdefault(‘name‘,‘太白‘)#有就不會變
 

# print(dic)

結果:

3. 刪

.pop 按key刪除,有返回值,並且如果沒有此key,可設置返回值.

dic = {"name":"jin","age":18,"sex":"male"}
ret = dic.pop(‘sex‘)
print(ret)
ret = dic.pop(‘sex1‘,‘沒有此鍵‘)
print(ret)

結果:

清空和刪除 clear是清空數據 字典還存在 del是刪除字典

dic = {"name":"jin","age":18,"sex":"male"}
dic.clear()
print(dic)
# del 刪除字典,刪除鍵值對
 

del dic
print(dic)

結果:

.popitem()隨機刪除一個數據,並產生返回值. 但是python3.6版本以後默認刪除最後一個數據

dic = {"name":"jin","age":18,"sex":"male"}
#popitem()  隨機刪除
ret = dic.popitem()
print(ret)
print(dic)

結果:

4. 改

dic = {"name":"jin","age":18,"sex":"male"}
# 改
#dic[‘key‘] = value
# 有key 就覆蓋.
dic["name"]=(1)

結果:

update 將dic的鍵值對,覆蓋,添加到dic2 中,dic不變

update 將dic的鍵值對,覆蓋,添加到dic2 中,dic不變
dic = {"name":"jin","age":18,"sex":"male"}
dic2 = {"name":"alex","weight":75}
dic2.update(dic)
print(dic)
print(dic2)

結果:

5 查
 .get方法通過key找值,如果沒有可以加值告知 不添加默認為none

dic = {"name":"jin","age":18,"sex":"male"}
# 查
print(dic[‘name‘])     #輸入key 找對應value
print(dic.get(‘name‘)) 
print(dic.get(‘name2‘,‘沒有此鍵值對‘))
print(dic)

結果:

a,b能同時賦值,只要後面有兩個元素, int list dict tuple等類型都行

a = 1      #一行代碼實現a,b值互換
b = 3
a,b = b,a
print(a,b)
a,b = [‘alex‘,‘wusir‘]
print(a,b)
a,b = (‘alex‘,‘wusir‘)
print(a,b)

結果:

6 找出所有key

dic = {"name":"jin","age":18,"sex":"male"}
for k in dic:
    print(k)
for k in dic.keys():  
    print(k)

7 找出所有values

dic = {"name":"jin","age":18,"sex":"male"}
for v in dic.values():
    print(v)

結果:

8 找出所有鍵值對;

dic = {"name":"jin","age":18,"sex":"male"}
for k,v in dic.items():
    print(k,v)

for k in dic:
    print(k,dic[k])

結果:

9 字典的嵌套

dic = {
    ‘name‘:‘金鑫‘,
    ‘name_list‘:[1,2,3,‘李傑‘],
    1:{
        ‘python10‘:[‘小黑‘,‘萌哥‘],
       ‘老男孩‘:{‘name‘:‘oldboy‘,‘age‘:56}
    }
}
#1,[1,2,3,‘李傑‘]追加‘wusir‘
#2, [‘小黑‘,‘萌哥‘] 小黑 萌哥中間 插入一個花哥
#3, {‘name‘:‘oldboy‘,‘age‘:56} 添加一個鍵值對,hobby:男人

dic[‘name_list‘].append(‘wusir‘)
print(dic)
l = dic[1][‘python10‘]
l.insert(1,‘花哥‘)
print(dic)
dic1 = dic[1]
dic2 = dic1[‘老男孩‘]
dic2[‘hobby‘] = ‘男人‘

結果:

字典的增刪改查和嵌套