python3.7入门系列六字典

比眉伴天荒 2022-02-05 13:51 288阅读 0赞

字典 是一系列键值对，如：

>>> person = \{'name' : 'jack', 'age' : 18\}  
>>> person\['age'\]  
18  
值可以是数字、字符串、列表、字典以及任何python类型的数据  
添加键值  
>>> person\['height'\] = 175  
>>> print(person)  
\{'name': 'jack', 'age': 18, 'height': 175\}

空字典  
>>> person = \{\}  
>>> person\['name'\] = 'Tom'  
>>> print(person)  
\{'name': 'Tom'\}  
修改值  
>>> person\['name'\] = 'Tommy'  
>>> print(person)  
\{'name': 'Tommy'\}

删除键值对  
>>> del person\['name'\]  
>>> print(person)  
\{\}

遍历字典  
利用字典的items(), keys(), values() 方法进行遍历  
>>> person = \{'name' : 'Tom', 'age' : 18, 'height' : 175\}  
>>> for item in person.items():  
...     print(item)  
...  
('name', 'Tom')  
('age', 18)  
('height', 175)  
可以发现每一个item是一个元组，可以用print(type(item))进行验证  
>>>  
>>> for key, value in person.items():  
...     print(key + ':' + str(value))  
...  
name:Tom  
age:18  
height:175  
>>> for key in person.keys():  
...     print(key)  
...  
name  
age  
height  
>>> for value in person.values():  
...     print(value)  
...  
Tom  
18  
175

嵌套  
>>> person1 = \{'name' : 'Tom', 'age' : 18, 'height' : 170\}  
>>> person2 = \{'name' : 'Jack', 'age' : 20, 'height' : 178\}  
>>> person3 = \{'name' : 'Rose', 'age' : 18, 'height' : 166\}  
>>> persons = \[person1, person2, person3\]  
>>> print(persons)  
\[\{'name': 'Tom', 'age': 18, 'height': 170\}, \{'name': 'Jack', 'age': 20, 'height' : 178\}, \{'name': 'Rose', 'age': 18, 'height': 166\}\]

>>> cities1 = \['beijing', 'shanghai'\]  
>>> cities2 = \['shanghai', 'hangzhou', 'nanjing'\]  
>>> favorite\_cities = \{'xiaoming' : cities1, 'xiaowang' : cities2\}  
>>> print(favorite\_cities)  
\{'xiaoming': \['beijing', 'shanghai'\], 'xiaowang': \['shanghai', 'hangzhou', 'nanjing'\]\}

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