Getting only those values that fulfill a condition in a numpy array

Question

There must a be a (very) quick and efficient way to get only elements from a numpy array, or even more interestingly from a slice of it. Suppose I have a numpy array:

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Answer 1

I'm aware that this is an old question, and I'm not sure if the following was available at the time it was asked, but since I got here with a similar question, this is what I found that worked for me:

np.extract(a[s] > 0, a[s])