panda的group by 和mysql的group by 相类似都是分组的功能
1 统计ABC的和
![](https://img.haomeiwen.com/i12079082/4c9c52290d1c267b.png)
2 统计ABC的平均值
![](https://img.haomeiwen.com/i12079082/3f42f10a4ddcdac7.png)
3 求男女的平均年龄
![](https://img.haomeiwen.com/i12079082/d8dfff231369b96e.png)
4 另外一种插入数据的方法,除了字典形式的插入,先指定值,再指定索引,再指定列名,相当于key值
![](https://img.haomeiwen.com/i12079082/34ed32a506c72dc9.png)
5 四则运算和numpy一样,默认是纵向相加,但是可以指定维度。还可以指定列这点和numpy不一样
![](https://img.haomeiwen.com/i12079082/544d8f10e3880503.png)
![](https://img.haomeiwen.com/i12079082/d01342b4b15ec781.png)
6 group by 延伸
![](https://img.haomeiwen.com/i12079082/7d7c38df5c6714aa.png)
![](https://img.haomeiwen.com/i12079082/1fae87bce9cabb40.png)
7 根据X分组后,有A.B两列。只显示A或者只显示B
![](https://img.haomeiwen.com/i12079082/0f0139d5b285d89b.png)
![](https://img.haomeiwen.com/i12079082/d7132978bc39a304.png)
8 Groupby后面可以跟函数
![](https://img.haomeiwen.com/i12079082/7990f2ed01b5dc6b.png)
9 同时以arrays和names两列作为索引
![](https://img.haomeiwen.com/i12079082/4617f2db76a0c1f5.png)
10 按照指定列进行聚合
![](https://img.haomeiwen.com/i12079082/d539f28df212f0d5.png)
![](https://img.haomeiwen.com/i12079082/dbeff2a8db04c22a.png)
11 将分组后的内容指定成索引和不指定成索引的区别
![](https://img.haomeiwen.com/i12079082/b779af72bc6f0be6.png)
![](https://img.haomeiwen.com/i12079082/21c3570df2657af1.png)
12
![](https://img.haomeiwen.com/i12079082/b895287b47d63386.png)
![](https://img.haomeiwen.com/i12079082/832d120575078827.png)
![](https://img.haomeiwen.com/i12079082/771e49323df6c7aa.png)
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