Pandas合并

﹏ヽ暗。殇╰゛Y 2023-06-03 02:49 24阅读 0赞

## **pd.concat实现数据合并** ##

*  pd.concat(\[data1, data2\], axis=1)
    
     *  按照行或列进行合并axis=0为列索引，axis=1为行索引  
        ![1552472-20190909200055791-38535438.png][]

## pd.merge ##

*  pd.merge(left, right, how='inner', on=None, left\_on=None, right\_on=None)
    
     *  可以指定按照两组数据的共同键值对合并或者左右各自  
        
     *  left: A DataFrame object
     *  right: Another DataFrame object
     *  on: Columns (names) to join on. Must be found in both the left and right DataFrame objects.
     *  left\_on=None, right\_on=None：指定左右键

how -- 以何种方式连接  
on -- 连接的键的依据是哪几个

<table> 
 <thead> 
  <tr> 
   <th>Merge method</th> 
   <th>SQL Join Name</th> 
   <th>Description</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>left</td> 
   <td>LEFT OUTER JOIN</td> 
   <td>Use keys from left frame only</td> 
  </tr> 
  <tr> 
   <td>right</td> 
   <td>RIGHT OUTER JOIN</td> 
   <td>Use keys from right frame only</td> 
  </tr> 
  <tr> 
   <td>outer</td> 
   <td>FULL OUTER JOIN</td> 
   <td>Use union of keys from both frames</td> 
  </tr> 
  <tr> 
   <td>inner</td> 
   <td>INNER JOIN</td> 
   <td>Use intersection of keys from both frames</td> 
  </tr> 
 </tbody> 
</table>

left = pd.DataFrame({'key1': ['K0', 'K0', 'K1', 'K2'], 'key2': ['K0', 'K1', 'K0', 'K1'], 'A': ['A0', 'A1', 'A2', 'A3'], 'B': ['B0', 'B1', 'B2', 'B3']}) right = pd.DataFrame({'key1': ['K0', 'K1', 'K1', 'K2'], 'key2': ['K0', 'K0', 'K0', 'K0'], 'C': ['C0', 'C1', 'C2', 'C3'], 'D': ['D0', 'D1', 'D2', 'D3']}) # 默认内连接 result = pd.merge(left, right, on=['key1', 'key2'])

![1552472-20190909201414240-211167250.png][]

*  左连接

result = pd.merge(left, right, how='left', on=['key1', 'key2'])

![1552472-20190909201457020-499121089.png][]

*  右连接

result = pd.merge(left, right, how='right', on=['key1', 'key2'])

![1552472-20190909201538513-1449028553.png][]

*  外连接

result = pd.merge(left, right, how='outer', on=['key1', 'key2'])

![1552472-20190909201600358-1880720389.png][]

转载于:https://www.cnblogs.com/oklizz/p/11493953.html

[1552472-20190909200055791-38535438.png]: /images/20230601/8760ca1b1b2742fb8a6e36a1f3b95421.png
[1552472-20190909201414240-211167250.png]: /images/20230601/05aeba315c734620ac6224e4f08a535d.png
[1552472-20190909201457020-499121089.png]: /images/20230601/a2bbd168bcc34f4493bc154fbaf06035.png
[1552472-20190909201538513-1449028553.png]: /images/20230601/f0d7ac45bf9b43c3b3dd2b80df44613b.png
[1552472-20190909201600358-1880720389.png]: /images/20230601/c2b04e2208574ea0a551c56574b1e43f.png