擅长:python、mysql、java
<p>你也可以这样使用<a href="https://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.pivot.html" rel="nofollow noreferrer">pivot</a>。看起来更干净</p>
<pre><code>df
id value count
0 1 groupA 2
1 2 groupB 1
2 1 groupB 3
3 1 groupC 1
4 3 groupC 2
5 2 groupA 1
6 3 groupA 5
aa = pd.DataFrame(df.groupby(by=["id", "value"]).sum()).reset_index().pivot(index="id", columns="value", values="count").fillna(0)
aa.columns.name = aa.index.name
aa.index.name = ""
aa
id groupA groupB groupC
1 5.0 3.0 1.0
2 1.0 1.0 0.0
3 5.0 0.0 2.0
</code></pre>