擅长:python、mysql、java
<p>在<code>sort_values</code>之前<code>transform</code><code>first</code></p>
<pre><code>df=df.sort_values(['Date','cost'])
df['maxCost']=df.groupby(['name','pid'])['cost'].transform('last')
df=df.sort_index()
df
Out[775]:
name pid cost Date maxCost
0 a 1 800 1991-01-31 400
1 b 2 200 1991-01-31 200
2 c 3 300 1991-01-31 600
3 a 1 400 2001-01-31 400
4 b 4 500 2001-01-31 500
5 c 3 600 2001-01-31 600
</code></pre>