Efficient way to count unique elements in array in numpy/scipy in Python

Question

I have a scipy array, e.g.

a = array([[0, 0, 1], [1, 1, 1], [1, 1, 1], [1, 0, 1]])

I want to count the number of occurrences of each unique ele

Answer 1

The numpy_indexed package (disclaimer: I am its author) provides a solution similar to the one posted by chuck; which is a nicely vectorized one. But with tests, a nice interface, and many more related useful functions:

import numpy_indexed as npi
npi.count(a)