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Pandas Column containing a list of matched strings found using str.contains('|'.join(words))

August 22, 2023

I have string data that I am matching to a list of terms and I want to create a new column that shows all words found in each row of the dataframe

df = pd.DataFrame({'String': ['Cat Dog Fish', 'Cat Dog', 'Pig Horse', 'DogFish']})
print(df)

         String
0  Cat Dog Fish
1       Cat Dog
2     Pig Horse
3       DogFish
4      CatHorse

words = ['Cat', 'Dog', 'Fish']

I know using df.loc[df['String'].str.contains('|'.join(words))].copy() will return all rows that contain at least one of the terms I’m searching for but I would like output that keeps a record of which terms are found in each string like this:

         String           Matched
0  Cat Dog Fish  [Cat, Dog, Fish]
1       Cat Dog        [Cat, Dog]
2       DogFish       [Dog, Fish]
3      CatHorse             [Cat]

or even just

         String     Matched
0  Cat Dog Fish  CatDogFish
1       Cat Dog      CatDog
2       DogFish     DogFish
3      CatHorse         Cat

Not sure where to begin with making this column, any help is appreciated

>Solution :

Try:

words = ["Cat", "Dog", "Fish"]

df["Matched"] = df["String"].apply(lambda s: [w for w in words if w in s])
print(df)

Prints:

         String           Matched
0  Cat Dog Fish  [Cat, Dog, Fish]
1       Cat Dog        [Cat, Dog]
2     Pig Horse                []
3       DogFish       [Dog, Fish]