Python Pandas - Merge based on substring in string

Question

I have 2 dataframes with the following format:

df_search

SEARCH
part1
anotherpart
onemorepart


df_all

FILE             EXTENSION    PATH
part1_1         .         


        

Answer 1

Use str.extract + insert:

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

Answer 2

I will do it in this way:

df_all['SEARCH'] = ''
for val in df_search.SEARCH:
    df_all.loc[df_all['FILE'].str.match(val), 'SEARCH'] = val