finding indexes with where clause over multiple values

Question

np.where(A ==2)[0]

gives the indexes of A where elements are equal to 2.

How do you generalize to a list of possible values?

I am looking for something like:

np.where(A in ([2,3,6,8]))[0]

Possible duplicate of Numpy - check if elements of a array belong to another array — miradulo
– miradulo, Commented Feb 24, 2018 at 22:35
Or another duplicate: Numpy mask based on if a value is in some other list — miradulo
– miradulo, Commented Feb 24, 2018 at 22:40

Stephen Rauch · Accepted Answer · 2018-02-24 22:36:24Z

1

Since NumPy 1.13 you can use the isin function.

In prior versions there was in1d.

A = np.array([1, 2, 3, 4, 5])
print(np.isin(A, [2, 3, 6, 8]))

[False  True  True False False]

answered Feb 24, 2018 at 22:36

Stephen Rauch♦

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