python counting elements in iterable with filter

Question

To count the elements in a list, you can use collections.Counter, but what if only some of the elements have to be counted?

I\'ve set up this example (please note: numpy

Answer 1

If this is about large numpy arrays you'd better take advantage of vectorized numpy operations.

%%time
np.unique(numbers[numbers <= 10], return_counts=True)

Output:

Wall time: 31.2 ms

(array([ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10]),
 array([10055, 10090,  9941, 10002,  9994,  9989, 10070,  9859, 10038,
        10028,  9965], dtype=int64))

​For comparison, my own timing of your code gave slighly higher times than yours.