CODEWITHSUNDEEP
python
Rolando
Rolando

Reputation: 62704

How to check if any item in a list occurs in another list?

If I have the following list:

listA = ["A","Bea","C"]

and another list

listB = ["B","D","E"]
stringB = "There is A loud sound over there"

What is the best way to check if any item in listA occurs in listB or stringB, if so then stop? I typically use for loop to iterate over each item in listA to do such a thing, but are there better ways syntactically?

for item in listA:
    if item in listB:
        break;

Upvotes: 4

Views: 2036

Answers (2)

Ashwini Chaudhary
Ashwini Chaudhary

Reputation: 251146

You can use any here: any will short-circuit and will stop at the first match found.

>>> listA = ["A","B","C"]
>>> listB = ["B","D","E"]
>>> stringB = "There is A loud sound over there"
>>> lis = stringB.split()
>>> any(item in listA or item in lis for item in listA) 
True

If listBis huge or the list returned from stringB.split() is huge then you should convert them to sets first to improve complexity:

>>> se1 =  set(listB)
>>> se2 = set(lis)
>>> any(item in se1 or item in se2 for item in listA)
True

If you're searching for multiple words inside that string then use regex:

>>> import re
>>> listA = ["A","B","C"]
>>> listB = ["B","D","E"]
>>> stringB = "There is A loud sound over there"
>>> any(item in listA or re.search(r'\b{}\b'.format(item),stringB)
                                                              for item in listA)

Upvotes: 1

David Robinson
David Robinson

Reputation: 78630

For finding the overlap of two lists, you can do:

len(set(listA).intersection(listB)) > 0

In if statements you can simply do:

if set(listA).intersection(listB):

However, if any items in listA are longer than one letter, the set approach won't work for finding items in stringB, so the best alternative is:

any(e in stringB for e in listA)

Upvotes: 9

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