擅长:python、mysql、java
<p>IIUC您需要首先在<code>fea1</code>上<code>sort</code>,然后在其上创建一个组号,以便<code>groupby</code>:</p>
<pre><code>df = df.sort_values("fea1")
df["group"] = df.groupby(df["fea1"].str[0]).cumcount()//3
print (df.groupby([df["fea1"].str[0], "group"])["fea2"].sum())
fea1 group
a 0 27
1 16
2 7
u 0 9
</code></pre>