Question

Given a list

[1,2,3,4,5,6]

with 2n elements

How do I get the list

[1+2,3+4,5+6]

with n elements?

Answer 1

From the itertools recipes section:

def grouper(n, iterable, fillvalue=None):
    "Collect data into fixed-length chunks or blocks"
    # grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx
    args = [iter(iterable)] * n
    return izip_longest(fillvalue=fillvalue, *args)

then call with:

for paired in grouper(2, inputlist):
    # paired is a tuple of two elements from the inputlist at a time.

grouper returns an iterator; if you have to have a list, simply consume the iterable into a new list:

newlist = list(grouper(2, inputlist))