在 Pandas 系列中搜索值列表并屏蔽匹配项

Question

I am trying to search for a list of values within a Pandas series and write the matches to a new column.

input:

vals = ['john', 'jane']

col1         
john doe
jane doe
billy j. 

desired output:

col1          col2
john doe      john
jane doe      jane
billy j.      nan

I tried to stay away from for loops and do it with Pandas methods but could not get the result.

With the bare python code below, I can print the matches but can't write them to the corresponding rows in col2. Also, it is obviously not efficient for larger datasets.

for i in vals:
    for j in df.col1:
        if i in j:
            print("match\t",  i,'in:\t',j)
        else:
            print('-')

output:
match    john in:    john doe
-
-
-
match    jane in:    jane doe
-

Any help would be appreciated.

Answer 1

Here's an option that could also handle multiple vals per row, concatenating them with comma:

df['col2'] = df.col1.apply(lambda x: ','.join([v for v in vals if v in x])).replace('', np.nan)

Output:

       col1  col2
0  john doe  john
1  jane doe  jane
2  billy j.   NaN

---

Another option using pandas.Series.findall :

pat = '|'.join(vals)
df['col2'] = df.col1.str.findall(pat).apply(','.join)