擅长:python、mysql、java
<p>你在正确的轨道上。在</p>
<pre><code>m = df.groupby(['CategoryA', 'CategoryB']).transform('sum').gt(0)
df['decision'] = np.where(m, 'keep', 'delete')
df
CategoryA CategoryB Count decision
0 1 A 0 delete
1 1 A -1 delete
2 2 B 1 keep
3 2 B 1 keep
4 3 C 1 delete
5 3 C -1 delete
</code></pre>
<p>使用<code>transform</code>检索相同大小的结果。在</p>