<p>您可以使用<code>pandas.melt</code>和<code>groupby</code>完成此操作:</p>
<pre><code>In [123]: molten = pd.melt(df, id_vars='name', var_name='last_referred')
In [124]: molten
Out[124]:
name last_referred value
0 bill action_1 referred
1 bob action_1 introduced
2 mary action_1 introduced
3 june action_1 introduced
4 dale action_1 referred
5 donna action_1 introduced
6 bill action_2 referred
7 bob action_2 referred
8 mary action_2 NaN
9 june action_2 referred
10 dale action_2 NaN
11 donna action_2 NaN
12 bill action_3 NaN
13 bob action_3 referred
14 mary action_3 NaN
15 june action_3 NaN
16 dale action_3 NaN
17 donna action_3 NaN
In [125]: gb = molten.groupby('name')
In [126]: col = gb.apply(lambda x: x[x.value == 'referred'].tail(1)).last_referred
In [127]: col.index = col.index.droplevel(1)
In [128]: col
Out[128]:
name
bill action_2
bob action_3
dale action_1
june action_2
Name: last_referred, dtype: object
In [129]: newdf = df.join(col, on='name')
In [130]: newdf
Out[130]:
name action_1 action_2 action_3 last_referred
0 bill referred referred NaN action_2
1 bob introduced referred referred action_3
2 mary introduced NaN NaN NaN
3 june introduced referred NaN action_2
4 dale referred NaN NaN action_1
5 donna introduced NaN NaN NaN
</code></pre>