How do I identify sequences of values in a boolean array?

Question

I have a long boolean array:

bool_array = [ True, True, True, True, True, False, False, False, False, False, True, True, True, False, False, True, True, True         


        

Answer 1

This will tell you where:

>>> import numpy as np
>>> np.argwhere(np.diff(bool_array)).squeeze()
array([ 4,  9, 12, 14, 18])

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np.diff calculates the difference between each element and the next. For booleans, it essentially interprets the values as integers (0: False, non-zero: True), so differences appear as +1 or -1 values, which then get mapped back to booleans (True when there is a change).

The np.argwhere function then tells you where the values are True --- which are now the changes.