Iterate a list as pair (current, next) in Python

Question

I sometimes need to iterate a list in Python looking at the \"current\" element and the \"next\" element. I have, till now, done so with code like:

for curre         


        

Answer 1

Since the_list[1:] actually creates a copy of the whole list (excluding its first element), and zip() creates a list of tuples immediately when called, in total three copies of your list are created. If your list is very large, you might prefer

from itertools import izip, islice
for current_item, next_item in izip(the_list, islice(the_list, 1, None)):
    print(current_item, next_item)

which does not copy the list at all.