Question

I have a long list with N elements. I would like to iterate the long list, but picking K elements at every iteration (or less if there are less than K in the long list). What would be the most elegant way to do it?

for short_list_K in long_list_N:
    # len(short_list_K) <= K

Answer 1

The itertools module documentation provides this recipe:

def grouper(n, iterable, fillvalue=None):
    "grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx"
    args = [iter(iterable)] * n
    return zip_longest(*args, fillvalue=fillvalue)

Which can be used like so:

for short_list in grouper(K, long_list):
      # blah