How to check a substring in dataframe included in a long string variable?

Question

My question is a different way as we usually check string by using str.contains(). I want to check if a substring in the dataframe is contained in a long string variable.

The dataframe looks like this:

Account	Substring	Category
1001	Cash Payment	Category #1
1002	Credit Card Payment	Category #2

The long string variable is long_str = “Cash Payment by Customer”.

So when using .loc to search/filter records in dataframe tha the substring that is contained in the long_str, is there any similar function like str.contains() but in the opposite way?

Below is the code I want to try to filter the dataframe, except str.contains() that won’t work. Thanks!

df.loc[df[‘Substring’].str.contains(long_str)]

Ank · Accepted Answer · 2021-06-17 14:55:41Z

1

You can simply use pandas.Series.apply method for that:

>>> long_str = "Cash Payment by Customer"
>>> df.loc[df.Substring.apply(lambda x: x in long_str)]
   Account     Substring     Category
0     1001  Cash Payment  Category #1

answered Jun 17, 2021 at 14:55

Ank

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2 Comments

Xavier Sun Over a year ago

Hi @ank, thank you so much ! This is working..i didn’t really we can use the apply function within the .loc[]. The only problem from that is the performance when we have millions of records to search, wondering if there will be any better solution with better performance? Thank you so much!

Ank Over a year ago

Hi @XavierSun . Not aware of any better solution for this. However a faster solution could be to use list comprehension directly instead of using the apply method. Give this a try and check the performance: df.loc[[x in long_str if x is not None else False for x in df.Substring]]

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