如何使这个简单的列表理解？

Question

I'm new to python, and I'm trying to get to know the list comprehensions better.
I'm not even really sure if list comprehension is the word I'm looking for, since I'm not generating a list. But I am doing something similar.

This is what I am trying to do:

I have a list of numbers, the length of which is divisible by three.

So say I have nums = [1, 2, 3, 4, 5, 6] I want to iterate over the list and get the sum of each group of three digits. Currently I am doing this:

for i in range(0, len(nums), 3):
    nsum = a + b + c for a, b, c in nums[i:i+3]
    print(nsum)

I know this is wrong, but is there a way to do this? I'm sure I've overlooked something probably very simple... But I can't think of another way to do this.

Answer 1

See sum(iterable[, start] ) builtin, and use it on slices.

Sums start and the items of an iterable from left to right and returns the total. start defaults to 0. The iterable's items are normally numbers, and are not allowed to be strings.

>>> nums
[1, 2, 3, 4, 5, 6]
>>> [sum(nums[i:i+3]) for i in  range(0, len(nums),3)]
[6, 15]
>>> 

Answer 2

import itertools

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

print [a + b + c for a, b, c in itertools.izip(*[iter(nums)] * 3)]

Answer 3

nums = [1, 2, 3, 4, 5, 6]
map(sum, itertools.izip(*[iter(nums)]*3))