How to filter a numpy array using another array's values?

Question

I have two NumPy arrays, e.g.:

a = [1,2,3,4,5]

and a filter array, e.g.:

f = [False, True, False, False, True]

len(a) == l         


        

Answer 1

If you don't already need numpy arrays, here's with a plain list:

import itertools
print itertools.compress(a, f)

For pre-2.7 versions of python, you must roll your own (see manual):

def compress(data, selectors):
    return (d for d, s in itertools.izip(data, selectors) if s)

Answer 2

NumPy supports boolean indexing

a[f]

This assumes that a and f are NumPy arrays rather than Python lists (as in the question). You can convert with f = np.array(f).