按两列分组并添加列

Question

假设我有下表，

+-------+----------+-------+-------+
| Date  | Exchange | price |     x | 
+-------+----------+-------+-------+
| 02/12 | LSE      |     1 |  s    |
| 03/12 | LSE      |     2 |  d    |
| 03/12 | LSE      |     2 |  f    |
| 03/12 | CBOE     |     3 |  q    |
| 04/12 | CBOE     |     4 |  w    |
| 04/12 | CBOE     |     5 |  t    |
+-------+----------+-------+-------+       

我想得到一个在两列日期和交换相同时添加价格列的表，即该表看起来像

+-------+----------+-------+
| Date  | Exchange | price |  
+-------+----------+-------+
| 02/12 | LSE      |     1 |  
| 03/12 | LSE      |     4 | 
| 03/12 | CBOE     |     3 |  
| 04/12 | CBOE     |     9 |  
+-------+----------+-------+

我尝试了一些但是没用

spread_per_isin_size_2500.groupby(['exchange', 'date']).size().groupby(level=1).max()

我能做到吗？

谢谢