<p>使用<a href="http://pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.str.extract.html" rel="noreferrer">^{<cd1>}</a>+<a href="http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.insert.html" rel="noreferrer">^{<cd2>}</a>:</p>
<pre><code>pat = "|".join(df_search.SEARCH)
df_all.insert(0, 'SEARCH', df_all['FILE'].str.extract("(" + pat + ')', expand=False))
print (df_all)
SEARCH FILE EXTENSION PATH
0 part1 part1_1 .prt //server/folder1/part1_1
1 part1 part1_2 .prt //server/folder2/part1_2
2 part1 part1_2 .pdf //server/folder3/part1_2
3 part1 part1_3 .prt //server/folder2/part1_3
4 anotherpart anotherpart_1 .prt //server/folder1/anotherpart_1
5 anotherpart anotherpart_2 .prt //server/folder3/anotherpart_2
6 anotherpart anotherpart_3 .prt //server/folder2/anotherpart_3
7 anotherpart anotherpart_3 .cgm //server/folder1/anotherpart_3
8 anotherpart anotherpart_4 .prt //server/folder3/anotherpart_4
9 onemorepart onemorepart_1 .prt //server/folder2/onemorepart_1
10 onemorepart onemorepart_2 .prt //server/folder1/onemorepart_2
11 onemorepart onemorepart_2 .dwg //server/folder2/onemorepart_2
12 onemorepart onemorepart_3 .prt //server/folder1/onemorepart_3
13 onemorepart onemorepart_4 .prt //server/folder1/onemorepart_4
</code></pre>