How to make a boolean array by checking if the ite…

I’m trying to find every item in an numpy array arr that’s also in an arbitrary list lst and replace them, but while arr > 0 will generate a boolean array for easy masking, arr in lst only works with all() or any() which isn’t what I need.

Example input: array (1, 2, 3, 4, 5), list [2, 4, 6, 8]

Output: array (1, 0, 3, 0, 5)

I managed to get the same result with for loops:

for i in range(len(arr)):
    if arr[i] in lst:
        arr[i] = 0

Just wondering if there are other ways to do it that set arrays apart from lists.

Answer

You can use numpy.isin:

a = np.array((1, 2, 3, 4, 5))
lst = [2, 4, 6, 8]
a[np.isin(a, lst)] = 0

Gives you an a of:

array([1, 0, 3, 0, 5])

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Answer