6

I'm looking for a way to check whether one string can be found in another string. str.contains only takes a fixed string pattern as argument, I'd rather like to have an element-wise comparison between two string columns.

import pandas as pd

df = pd.DataFrame({'long': ['sometext', 'someothertext', 'evenmoretext'],
               'short': ['some', 'other', 'stuff']})


# This fails:
df['short_in_long'] = df['long'].str.contains(df['short'])

Expected Output:

[True, True, False]
E. Sommer
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4 Answers4

6

Use list comprehension with zip:

df['short_in_long'] = [b in a for a, b in zip(df['long'], df['short'])]

print (df)
            long  short  short_in_long
0       sometext   some           True
1  someothertext  other           True
2   evenmoretext  stuff          False
jezrael
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3

This is a prime use case for a list comprehension:

# df['short_in_long'] = [y in x for x, y in df[['long', 'short']].values.tolist()]
df['short_in_long'] = [y in x for x, y in df[['long', 'short']].values]
df

            long  short  short_in_long
0       sometext   some           True
1  someothertext  other           True
2   evenmoretext  stuff          False

List comprehensions are usually faster than string methods because of lesser overhead. See For loops with pandas - When should I care?.

If your data contains NaNs, you can call a function with error handling:

def try_check(haystack, needle):
    try:
        return needle in haystack
    except TypeError:
        return False

df['short_in_long'] = [try_check(x, y) for x, y in df[['long', 'short']].values]
cs95
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3

Check with numpy, it is row-wise :-) .

np.core.char.find(df.long.values.astype(str),df.short.values.astype(str))!=-1
Out[302]: array([ True,  True, False])
BENY
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  • I used `numpy` a well. I was trying `df['short_in_long'] = np.where(df['short'].str.contains(df['long']), True, False)`. Why does this not work row-wise? – Erfan Mar 15 '19 at 14:22
  • @Erfan isin will not check the partial match :-) – BENY Mar 15 '19 at 14:23
  • Sorry, that was my second try. I edited my comment. – Erfan Mar 15 '19 at 14:24
  • @Erfan two part , `str.contain` do not accept `Series`, second , if you using join string with `sep = '|'` when the 3rd row have any partial string like `some` and `other`, the 3rd row will return as True under `str.contain` – BENY Mar 15 '19 at 14:29
  • Thank you, so when using `sep = '|'` It would check each row over the whole column. – Erfan Mar 15 '19 at 14:33
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    @Erfan yes that is why when do rowwise check like 1-1 , we can not using str.contains – BENY Mar 15 '19 at 14:34
1

Also,

df['short_in_long'] = df['long'].str.contains('|'.join(df['short'].values))

Update : I misinterpreted the problem. Here is the corrected version:

df['short_in_long'] = df['long'].apply(lambda x: True if x[1] in x[0] else False, axis =1)
Loochie
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