Pandas 操作数据（二）

蔚落 2024-04-07 14:01 9阅读 0赞

### 一、内置函数应用和映射 ###

<table> 
 <tbody> 
  <tr> 
   <td> <p>函数</p> </td> 
   <td> <p>用法</p> </td> 
  </tr> 
  <tr> 
   <td> <p>apply()</p> </td> 
   <td> <p>用于对DataFrame中的数据进行按行或者按列操作</p> </td> 
  </tr> 
  <tr> 
   <td> <p>map()</p> </td> 
   <td> <p>用于对Series中的每一个数据操作</p> </td> 
  </tr> 
  <tr> 
   <td> <p>applymap()</p> </td> 
   <td> <p>用于对DataFrame的每一个数据操作</p> </td> 
  </tr> 
 </tbody> 
</table>

**1、apply()函数 -对DataFrame 进行按行或者按列操作**

![939c7a3017ae437e94ab47e4abff70e3.png][]

![b2f0037e5f7e48c4ba93ed5cebedb88f.png][] ![7b2dd7b170b342eea5d9f06d25caff83.png][]

![d082cb34eb5e4efe8ad371f8fd5b4c5f.png][]

**2、applymap()-对DataFrame 每一个数据操作**

![39fb8a941d2d433b80dd44c654b5188f.png][]

![f0b9fdf763e9419fa272f31fd952a070.png][]

**3、map()-对Series中的每一个数据操作**

![c8c1be3ffab348bc91d0374827ed27aa.png][]

![5c98dbd8e7ce4cbfad780bbe8d1ba6fd.png][]

### 二、重复标签轴索引 ###

> df.index.is\_unique \# 判断是否是唯一值
> 
> df.index.unique() \# 获取唯一值

![5433da9aae4342788fccbda43ee010c1.png][]

### 三、数据添加 ###

1、直接添加数据列 
           df['e']=100
           df[['e','f']]=99    #必须再加[ ]
           df['score']=[75,99,65]  #添加一列成绩
    
    2、使用insert(位置，列名，值)添加数据列
            df.insert(2,'count',[5,10,5])
    
    3、使用append()添加，沿着 axis=0 （行方向）进行操作      
           #ignore_index=True 忽略原来的索引，新索引从0开始
           df1=df1.append(df2,ignore_index=True)

### 四、数据合并 ###

1、concat连接操作：有行和列拼接，默认是行拼接，
          拼接方法默认是外拼接（并集），拼接的对象是pandas数据类型
    
    
       2、merge合并操作：基于column连接dataframe
    
    
       3、 join() 合并操作：基于index连接dataframe
    
         2与3的连接方法有内连接，外连接，左连接和右连接

**1、concat连接操作**

![2b585634323d440d83326140da59cac1.png][]

![d67960202f8d42638ca8c52ce4bccc32.png][]

**2、merge合并操作**

![e53cc1632b0f4653ae8466591aee36c3.png][]

![6ee38a45252e44b09affb3c0bca10870.png][]

**使用how参数合并：**

![8c64263fbabf4eac88fab4207f81b6c7.png][]

**3、join合并操作**

![fd0d97a54a8c4445895d8e8d496c5c41.png][]![228277107d084427bf79fb506198e86d.png][]

![09836dd7a95a43348afaa59a14d1eae4.png][]

### 五、数据删除 ###

![49fb800529f4468ca461d8af1b04c07f.png][]

### 六、创建多级索引 ###

![f94a938ab69f4914b69a0b0ac6ff5f1e.png][]

![c99c851f63f447979858f455675e1a24.png][]

### 七、 检索多层索引 ###

![08c4779b58e74282bdca5f28199a0267.png][]

![24724cdbfff1425db46fcbc07c277d7e.png][]

![b8be58fce786473a9ff3d42dd417a0dc.png][]

### 八、更改索引层级 ###

![5afe3ea4d41c4b9089ea7c82225cfdaa.png][]

### 九、 算术运算和数据对齐 ###

### ![d3ec61c3a3bc424d93d6df542fb697db.png][] ###

![d74ec807299f48b88d447ef93d43b5f9.png][]

### 说明：两种结构之间的运算 ###

广播机制

![f0640518786d434f9a26375c6b0a8f38.png][]

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