day 10 字典dict

 

    添加
        xxx[新的key] = value
    
    删除
        del xx[key]
    
    修改
        xxx[已存在的key] = new_value
    
    查询
        xxx.get(key)

1. dict 字典

#### list 列表存储数据
In [4]: stu001 = ["alex",18,"北京"]

In [5]: print("%s的年龄是%d,家住在%s"%(stu001[0],stu001[1],stu001[2]))
alex的年龄是18,家住在北京


##### dict 字典存储数据
In [6]: #字典
In [7]: #info = {键:值，键:值}      key：value   键值对

In [8]: stu001 = {"name":"alex","age":18,"home":"beijing"}
In [12]: print("%s的年龄是%d,家在%s"%(stu001["name"],stu001["age"],stu001["home"]))
alex的年龄是18,家在beijing

2.增删改查

########   增加  xxx[新的key] = value
In [1]: infor = {"name":"alex"}

In [2]: infor["age"] = 18

In [3]: infor
Out[3]: {'name': 'alex', 'age': 18}


In [4]: infor["QQ"] = 10086

In [5]: infor
Out[5]: {'QQ': 10086, 'name': 'alex', 'age': 18}

#########  删除  del xxx[已存在的key]
#########  删除  del xxx[不存在的key]  报错

In [8]: del infor["QQ"]

In [9]: infor
Out[9]: {'name': 'alex', 'age': 18}


In [10]: del infor["QQ"]
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-10-1c0f878ade5a> in <module>()
----> 1 del infor["QQ"]

KeyError: 'QQ'

#########  修改  xxx[已存在的key] = new_value

In [6]: infor["QQ"] = 8888

In [7]: infor
Out[7]: {'QQ': 8888, 'name': 'alex', 'age': 18}

#########  查询 不正确用法   infor["QQ"]
In [11]: infor
Out[11]: {'name': 'alex', 'age': 18}


In [12]: infor["name"]
Out[12]: 'alex'

In [13]: infor["age"]
Out[13]: 18


In [14]: infor["QQ"]
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-14-8398698e14db> in <module>()
----> 1 infor["QQ"]

KeyError: 'QQ'


######## 查询  标准用法   infor.get("QQ")

In [15]: infor.get("QQ")

In [16]: infor.get("name")
Out[16]: 'alex'

In [17]: infor.get("age")
Out[17]: 18