What does this: s[s[1:] == s[:-1]] do in numpy?

Question

I\'ve been looking for a way to efficiently check for duplicates in a numpy array and stumbled upon a question that contained an answer using this code.

What does th

Answer 1

Check this out:

>>> s=numpy.array([1,3,5,6,7,7,8,9])
>>> s[1:] == s[:-1]
array([False, False, False, False,  True, False, False], dtype=bool)
>>> s[s[1:] == s[:-1]]
array([7])

So s[1:] gives all numbers but the first, and s[:-1] all but the last. Now compare these two vectors, e.g. look if two adjacent elements are the same. Last, select these elements.