Efficient way of finding index of element of one array in another array without using pandas

Question

suppose I have two array arr1 and arr2

arr1 = ["ABC","DEF","GHI","XYZ"]

arr2 = ["ABC","XYZ"]

I need the index of element of arr2 in arr1.

required result =[0,3]

I am able to do this using pandas but need an effective way of doing maybe by numpy.

A = pd.series(arr1)
B = pd.series(arr2)

B.map(lambda x: np.where(A==x)[0][0]).tolist()

U13-Forward · Accepted Answer · 2021-09-02 07:32:36Z

1

Try np.where this way:

>>> np.where(np.isin(arr1, arr2))[0]
array([0, 3], dtype=int64)
>>>

If you want a list:

>>> np.where(np.isin(arr1, arr2))[0].tolist()
[0, 3]
>>>

answered Sep 2, 2021 at 7:32

U13-Forward

71.8k15 gold badges100 silver badges125 bronze badges

Sign up to request clarification or add additional context in comments.

1 Answer 1