数据类型-字典

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最有层次感的数据类型，特别干净整洁。在写爬虫时，我们最希望遇到的数据类型就是ta

下图就是最简单的字典的样式，键值对 key-value-pairs

字典

字典是有key，有value的 key-value-pair类型数据（键-值对）

将上面的员工信息以关键词name、age、hobbies 组织成字典数据

空字典

david = dict()
print(david)

{}

填充

david['age'] = 23
print(david)

{'age': 23}

david['hobbies'] = ['Basketball', 'Pingpang', 'Hiking']
print(david)

{'age': 23, 'hobbies': ['Basketball', 'Pingpang', 'Hiking']}

david['gender'] = 'Male'
print(david)

{'age': 23, 'hobbies': ['Basketball', 'Pingpang', 'Hiking'], 'gender': 'Male'}

更新

david['age'] = 25
print(david)

{'age': 25, 'hobbies': ['Basketball', 'Pingpang', 'Hiking'], 'gender': 'Male'}

完整的信息

infos =  {'David':{'age':25, 
                   'gender':'Male',
                   'hobbies':['Basketball', 'Pingpang', 'Hiking']},
          'Mary':{'age':23,
                  'gender': 'Female',
                  'hobbies': ['Reading', 'Movies']},
          'Henry':{'age':23,
                  'gender': 'Male',
                  'hobbies': ['Diving', 'Hiking']}
         }

print(infos)

{'David': {'age': 25, 'gender': 'Male', 'hobbies': ['Basketball', 'Pingpang', 'Hiking']}, 'Mary': {'age': 23, 'gender': 'Female', 'hobbies': ['Reading', 'Movies']}, 'Henry': {'age': 23, 'gender': 'Male', 'hobbies': ['Diving', 'Hiking']}}

字典的方法

infos.items()

dict_items([('David', {'age': 25, 'gender': 'Male', 'hobbies': ['Basketball', 'Pingpang', 'Hiking']}), ('Mary', {'age': 23, 'gender': 'Female', 'hobbies': ['Reading', 'Movies']}), ('Henry', {'age': 23, 'gender': 'Male', 'hobbies': ['Diving', 'Hiking']})])

#把infos.items()转化为列表
list(infos.items())[0]

('David',
 {'age': 25,
  'gender': 'Male',
  'hobbies': ['Basketball', 'Pingpang', 'Hiking']})

infos.keys()

dict_keys(['David', 'Mary', 'Henry'])

infos.values()

dict_values([{'age': 25, 'gender': 'Male', 'hobbies': ['Basketball', 'Pingpang', 'Hiking']}, {'age': 23, 'gender': 'Female', 'hobbies': ['Reading', 'Movies']}, {'age': 23, 'gender': 'Male', 'hobbies': ['Diving', 'Hiking']}])

print(infos['David'])
print(infos.get('David'))

{'age': 25, 'gender': 'Male', 'hobbies': ['Basketball', 'Pingpang', 'Hiking']}
{'age': 25, 'gender': 'Male', 'hobbies': ['Basketball', 'Pingpang', 'Hiking']}

注意： 两种功能等同，但是get获取方法更加安全稳定。

例如

print(infos['Will'])

---------------------------------------------------------------------------

KeyError                                  Traceback (most recent call last)

<ipython-input-16-f7c283c8ad8e> in <module>
----> 1 print(infos['Will'])


KeyError: 'Will'

print(infos.get('Will'))

None

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