CODEWITHSUNDEEP
python
bas
bas

Reputation: 25

Fastest way of comparing lists of strings

A = ['a','b','c'] 
B = ['d','b','e']

res = [i for i in A if i in B]

The above code does not work when the no of elements in A are 300000 and in B are 200000.

How can I solve it?

I also tried

res = {i for i in A if i in B}
res = list(res)

But still could not get the result.

Upvotes: 0

Views: 299

Answers (3)

Khaelex
Khaelex

Reputation: 762

If preserving order and/or duplicates doesn't matter, then you can use

A = ['a', 'b', 'c']
B = ['d', 'e', 'f']
res = list(set(A) & set(B))

If order and/or duplicates does matter, then you can use

A = ['a', 'b', 'c']
B = ['d', 'e', 'f']
set_b = set(B)
res = [i for i in A if i in set_b]

Upvotes: 3

Padraic Cunningham
Padraic Cunningham

Reputation: 180441

A = ['a','b','c']
B = ['d','b','e']

set(A).intersection(B)

To get a list returned:

list(set(A).intersection(B))

intersection takes any iterable as an argument so you just need to make A a set.

Note, the non-operator versions of union(), intersection(), difference(), and symmetric_difference() will accept any iterable as an argument.

Upvotes: 3

Sven Marnach
Sven Marnach

Reputation: 601789

You are basically computing the intersection of two sets. Using the set data type for this will make this efficient:

A = {'a','b','c'}
B = {'d','b','e'}
res = A & B

Upvotes: 1

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