字典

字典：简单讲就是无序的，可变的，可包含任意对象的“键值对”（key:value）的集合

特点：
1. 属于可变序列
2. 可变长度
3. 任意类型
4. 任意嵌套
5. 支持原位改变

定义字典
none_dict = {}  #定义一个空字典
user_info_dict = {"name":"马小跳","age":17,"gender":"male","job":"学神"}
print(none_dict)
print(user_info_dict)

运行结果: 

{}
{'name': '马小跳', 'age': 17, 'gender': 'male', 'job': '学神'}
字典的增删改查
修改：
user_info_dict = {"name":"马小跳","age":17,"gender":"male","job":"学神"}
print(user_info_dict)
user_info_dict["name"] = "马大哈"  #将name的value替换为"马大哈"
print(user_info_dict)

 ```  
运行结果:
{‘name’: ‘马小跳’, ‘age’: 17, ‘gender’: ‘male’, ‘job’: ‘学神’} 
 {‘name’: ‘马大哈’, ‘age’: 17, ‘gender’: ‘male’, ‘job’: ‘学神’}
###### 查询：  
```python  
user_info_dict = {"name":"马小跳","age":17,"gender":"male","job":"学神"}
print("%s的年龄是：%d,性别是:%s,工作:%s"%(user_info_dict["name"],user_info_dict["age"],user_info_dict["gender"],user_info_dict["job"]))




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#key不能相同，相同后面的会覆盖前面的
user_info_dict = {"name":"马小跳","age":17,"gender":"male","job":"学神","job":"学炸"}
print("工作:%s"%user_info_dict["job"])




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运行结果: 

马小跳的年龄是：17,性别是:male,工作:学神
工作:学炸




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添加：
user_info_dict = {"name":"马小跳","age":17,"gender":"male","job":"学神"}
user_info_dict["tel"] = "909272590"
print(user_info_dict)




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运行结果: 

{'name': '马小跳', 'age': 17, 'gender': 'male', 'job': '学神', 'tel': '909272590'}  




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删除：
user_info_dict = {"name":"马小跳","age":17,"gender":"male","job":"学神"}
del user_info_dict["job"]
print(user_info_dict)




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运行结果: 

{'name': '马小跳', 'age': 17, 'gender': 'male'}




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字典.keys() 来获取字典中的所有的键
user_info_dict = {"name":"马小跳","age":17,"gender":"male","job":"学神"}
for key in user_info_dict.keys():
    print(key)




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运行结果: 

name
age
gender
job




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字典.values() 来获取字典中所有的值
user_info_dict = {"name":"马小跳","age":17,"gender":"male","job":"学神"}
for values in user_info_dict.values():
    print(values)  




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运行结果: 

马小跳
17
male
学神  




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.items() 获取字典中的某个键值对返回一个元组

将字典里的键值对输出成元组，输出最后一个元组的第一个元素

user_info_dict = {"name":"马小跳","age":17,"gender":"male","job":"学神"}
for item in user_info_dict.items():
    print(item)
print(item[0])




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运行结果: 

('name', '马小跳')
('age', 17)
('gender', 'male')
('job', '学神')
job




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如果需要把每个元素都遍历出来可以再添加一个临时变量 

user_info_dict = {"name":"马小跳","age":17,"gender":"male","job":"学神"}
for key,value in user_info_dict.items():
    print(key)
    print(value)




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运行结果：

name
马小跳
age
17
gender
male
job
学神




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clear()清空字典
user_info_dict = {"name":"马小跳","age":17,"gender":"male","job":"学神"}
print(user_info_dict)
user_info_dict.clear()
print(user_info_dict)




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运行结果: 

{'name': '马小跳', 'age': 17, 'gender': 'male', 'job': '学神'}
{}




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通过value 取 key
user_info_dict = {"name":"马小跳","age":17,"gender":"male","job":"学神"}
key_list = list(user_info_dict.keys())  #将key转换为列表
value_list = list(user_info_dict.values())  #将value转换为列表
print(key_list)    #输出key列表
print(value_list)  #输出value列表
result = key_list[value_list.index("学神")]  #从value列表中查找"学神"的下标，再从key列表中查找以学神下标为下标的元素
print(result)  #输出这个元素  




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运行结果 ： 

['name', 'age', 'gender', 'job']
['马小跳', 17, 'male', '学神']
job




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从单个字典里取key
d = {"name":"悟空"}
key1,= d
print(key1)




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运行结果 ： 

name




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从多个字典中取key

注意:变量需要和字典中的key数量对应 

d = {"name":"悟空","my":1,"you":2}
key1,key2,key3 = d
print(key1,key2,key3)




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运行结果： 

name my you