You have multiple options. Two options are the following.
numpy.sum(boolarr)
numpy.count_nonzero(boolarr)
Here's an example:
>>> import numpy as np
>>> boolarr = np.array([[0, 0, 1], [1, 0, 1], [1, 0, 1]], dtype=np.bool)
>>> boolarr
array([[False, False, True],
[ True, False, True],
[ True, False, True]], dtype=bool)
>>> np.sum(boolarr)
5
Of course, that is a bool-specific answer. More generally, you can use numpy.count_nonzero.
>>> np.count_nonzero(boolarr)
5