if one of several strings are in other string: return a value + matching string, Python

Question

I would like to ask your help with an "if statement" inside a function that I am using to aggregate some data in a dataframe. With this function I wanted to check if any of several strings are in other string in one column of my dataframe to return an specific value and the matching string.

This is what I have so far and it does what I need. For example, if "f" and "k" are in my string ("fk"), once I apply my function on this row (find_string("fk")), my function will return "success". Additionally I would also like to have the string that was found in the list, in this case 'f'. Something like "success" + "f"

 def find_string(b):
     if "a"  in b or "c"  in b or "d"  in b or "f"  in b:
         return "success"  ## here I want to get the matching string

Any suggestion?

I am using python 2.7.13 with pandas library.

You mention a Dataframe, does the answer you are looking for need to pandas-specific? IF so, could you provide a small sample of your dataframe? There are functions/methods in pandas that are much faster than normal loops — MattR
– MattR, Commented Nov 2, 2017 at 12:54

cs95 · Accepted Answer · 2017-11-02 12:59:20Z

2

If you're using pandas, use str.extract + np.where, it's much faster.

v = df['yourCol'].str.extract('([acdf])', expand=False)
df['newCol'] = np.where(v.isnull(), '', 'success' + v.astype(str))

answered Nov 2, 2017 at 12:59

cs95

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2 Comments

jezrael Over a year ago

Nice solution :)

cs95 Over a year ago

@jezrael Thank you sir, appreciate it. :-)

Eric Duminil · Accepted Answer · 2017-11-02 13:13:27Z

1

You could simply use set intersections. It doesn't require any if or loops and should be very efficient:

>>> set('try to find a substring') & set('acdf')
{'a', 'f', 'd'}
>>> set('no substring') & set('acdf')
set()

If you really want to use pandas, look at @Coldspeed's solution.

answered Nov 2, 2017 at 13:13

Eric Duminil

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1 Comment

Elazar Over a year ago

This is the "right" way (in plain Python) but there's a step lacking for getting from the set to a "success f" or something similar, and it can be confusing for a beginner - what do I do with more than one? with zero? These questions are swept under the rug in the for implementation.

Elazar · Accepted Answer · 2017-11-02 13:24:11Z

1

def find_string(b):
   for c in ['a', 'c', 'd', 'f']:
       if c in b:
           return 'success ' + c
   return 'failure'

>>> find_string('fk')
'success f'

edited Nov 2, 2017 at 13:24

answered Nov 2, 2017 at 12:51

Elazar

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2 Comments

cs95 Over a year ago

This is a pandas question, and a pandas solution is required.

Elazar Over a year ago

@cᴏʟᴅsᴘᴇᴇᴅ I have fixed the OP code. A pandas solution such as yours is better, but this answer should still help the OP, which seems to be struggling with a plain Python implementation. (BTW the pandas tag was added by me).

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