Python: Adding within lists

Question

It may be the fact I haven't slept yet, but I can't find the solution to this problem, so I come to you all. I have a list, with a series of sub-lists, each containing two values, like so:

list = (
  (2, 5),
  (-1, 4),
  ( 7, -3)
  )

I also have a variable, a similar list with two values, that is as such:

var = (0, 0)

I want to add all the x values in list, then all the y values, and then store the sums in var, so the desired value of var is:

var = (8, 6)

How could I do it? I apologize if the answer is something stupid simple, I just need to get this done before I can sleep.

Joran Beasley · Accepted Answer · 2013-07-27 16:45:46Z

6

sumvar = map(sum,zip(*my_list))

should do what you want i think

answered Jul 27, 2013 at 16:45

Joran Beasley

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Comments

roman · Accepted Answer · 2013-07-27 17:32:24Z

0

This sounds like a job for "reduce" to me:

reduce(lambda a,b: (a[0]+b[0],a[1]+b[1]), list)
(8,6)

you could also use another list comprehension method, (a bit more readable):

sum(a for a,b in tpl), sum(b for a,b in tpl)
(8,6)

edited Jul 27, 2013 at 17:32

roman

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answered Jul 27, 2013 at 16:50

swstephe

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