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How to find the common elements in two or more lists in Python?

1 Answer

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There are several ways to find the common elements in two or more python lists. When you have only two lists, you can use one of the following approaches:

>>> a=[1, 2, 4, 3]
>>> b=[3,4,5,6]
>>> set(a).intersection(b)
{3, 4}
>>> [i for i in b if i in a]
[3, 4]
>>> import numpy as np
>>> np.intersect1d(a,b)
array([3, 4])

When you have more than two lists, you can use one of the following approaches:

>>> a=[1, 2, 4, 3]
>>> b=[3,4,5,6]
>>> c=[3,7,8,9,10]
>>> [i for i in c if i in a and i in b]
[3]
>>> set(a).intersection(c,b)
{3}
>>> from functools import reduce
>>> reduce(np.intersect1d,(a,b,c))
array([3])

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