python基礎2--字典

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字典

字典是另一種可變容器模型，且可儲存任意類型對象。

字典的每個索引值(key=>value)對用冒號(:)分割，每個對之間用逗號(,)分割，整個字典包括在花括弧({})中

文法：

1 goods = {2     ‘apple‘:4.5,3     ‘orange‘:2.3,4     ‘banana‘:3.55      }

字典的特性：

• dict是無序的
• key必須是唯一的

 

1.增加元素

1 >>> goods2 {‘apple‘: 4.5, ‘banana‘: 3.5, ‘orange‘: 2.3}3 >>> goods[‘peach‘]=5.04 >>> goods5 {‘apple‘: 4.5, ‘banana‘: 3.5, ‘orange‘: 2.3, ‘peach‘: 5.0}

2.修改

1 >>> goods[‘apple‘]=5.5  # 將蘋果的價格改為 5.52 >>> goods3 {‘apple‘: 5.5, ‘banana‘: 3.5, ‘orange‘: 2.3, ‘peach‘: 5.0}

3.刪除元素

 1 >>> goods 2 {‘apple‘: 5.5, ‘banana‘: 3.5, ‘orange‘: 2.3, ‘peach‘: 5.0} 3 >>> goods.pop(‘peach‘)    #刪除最後一個，並返回value的值 4 5.0 5 >>> goods 6 {‘apple‘: 5.5, ‘banana‘: 3.5, ‘orange‘: 2.3} 7  8 >>> del goods[‘banana‘]   # 指定 key的刪除 9 >>> goods10 {‘apple‘: 5.5, ‘orange‘: 2.3}11 12 >>> goods13 {‘apple‘: 5.5, ‘grape‘: 6.0, ‘orange‘: 2.3, ‘watermelon‘: 12.0}14 >>> goods.popitem()   # 隨機刪除15 (‘apple‘, 5.5)16 >>> goods17 {‘grape‘: 6.0, ‘orange‘: 2.3, ‘watermelon‘: 12.0}

4.尋找

 1 >>> goods 2 {‘grape‘: 6.0, ‘orange‘: 2.3, ‘watermelon‘: 12.0} 3 >>> ‘grape‘ in goods 4 True 5 >>> goods.get(‘orange‘)    # 知道key,擷取 value 6 2.3 7 >>> goods[‘watermelon‘] 8 12.0 9 >>> goods[‘apple‘]   # 如果一個key不存在,就會報錯，get不會，不存在只會返回None10 Traceback (most recent call last):11   File "<stdin>", line 1, in <module>12 KeyError: ‘apple‘

5.多級字典及操作

 1 area = {‘浙江‘: 2             { 3              ‘杭州‘:[‘西湖區‘,‘下城區‘,‘蕭山區‘], 4              ‘嘉興‘:[‘南湖區‘,‘秀洲區‘,‘平湖市‘], 5              ‘溫州‘:[‘九灣區‘,‘鹿城區‘,‘洞頭區‘] 6              }, 7         ‘江蘇‘: 8             { 9              ‘南京‘:[‘鼓樓區‘,‘玄武區‘,‘秦淮區‘],10              ‘蘇州‘:[‘姑蘇區‘,‘吳中區‘,‘虎丘區‘],11              ‘常州‘:[‘武進區‘,‘金壇市‘,‘溧陽市‘]12             }13 14 15         }16         17 >>> area[‘浙江‘][‘杭州‘]18 [‘西湖區‘, ‘下城區‘, ‘蕭山區‘]19 20 21 >>> area[‘浙江‘][‘杭州‘][1] += ‘,很大‘22 >>> area[‘浙江‘][‘杭州‘]23 [‘西湖區‘, ‘下城區,很大‘, ‘蕭山區‘]

6.其他用法

 1 >>> area.keys() 2 dict_keys([‘浙江‘, ‘江蘇‘]) 3 >>> goods.values() 4 dict_values([6.0, 2.3, 12.0]) 5 >>> goods.keys() 6 dict_keys([‘grape‘, ‘orange‘, ‘watermelon‘]) 7  8 {‘grape‘: 6.0, ‘orange‘: 2.3, ‘watermelon‘: 12.0} 9 >>> b = {1:2,3:4,‘grape‘:4.5}10 >>> goods.update(b)11 >>> goods12 {1: 2, 3: 4, ‘grape‘: 4.5, ‘orange‘: 2.3, ‘watermelon‘: 12.0}13 14 >>> goods.items()15 dict_items([(1, 2), (3, 4), (‘grape‘, 4.5), (‘orange‘, 2.3), (‘watermelon‘, 12.0)])

7.遍曆字典

1 for key in goods:2     print(key,goods[key])3 #或4 for k,v in goods.items():5     print(k,v)

 

python基礎2--字典