Adding values in a nested list [duplicate]

Question

Possible Duplicate:
Merging/adding lists in Python

nested_list= [[1, 3, 5], [3, 4, 5]]
sum_of_items_in_nested_list = [4, 7, 10]

I am trying to create a nested for loop that will add take the item at each corresponding index and add it to the other nested list at the same index. So the above adds nested_list[0][0] + nested_list[1][0], nested_list[0][1] + nested_list[1][1] and so on. I would like to do this without importing and modules. This is probably so easy but I am having the devil of a time with it.

What have you tried?

Sebastian Paaske Tørholm
– Sebastian Paaske Tørholm

2012-10-28 16:40:27 +00:00
Commented Oct 28, 2012 at 16:40 — Sebastian Paaske Tørholm
– Sebastian Paaske Tørholm, Commented Oct 28, 2012 at 16:40

Ashwini Chaudhary · Accepted Answer · 2012-10-28 16:56:02Z

4

use zip():

In [44]: nested_list= [[1, 3, 5], [3, 4, 5]]

In [45]: [sum(x) for x in zip(*nested_list)]
Out[45]: [4, 7, 10]

another way, using nested loops:

In [6]: nested_list= [[1, 3, 5], [3, 4, 5]]

In [7]: minn=min(map(len,nested_list))   #fetch the length of shorted list

In [8]: [sum(x[i] for x in nested_list) for i in range(minn)]
Out[8]: [4, 7, 10]

edited Oct 28, 2012 at 16:56

answered Oct 28, 2012 at 16:41

Ashwini Chaudhary

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3 Comments

spitfiredd Over a year ago

How would you do this with using a nested for loop? I am trying to understand how to do this and I am just not "getting it"

Ashwini Chaudhary Over a year ago

@user1761521 nested for loop is not required for this.

Ashwini Chaudhary Over a year ago

@user1761521 I've added another approach for doing this with nested loops.

hendrik · Accepted Answer · 2012-10-28 18:51:17Z

0

you may also think about this solution:

map(int.__add__,*nested_list)

Better style:

from operator import add
map(add,*nested_list)

edited Oct 28, 2012 at 18:51

answered Oct 28, 2012 at 18:39

hendrik

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Comments

mzn.rft · Accepted Answer · 2012-10-30 15:56:49Z

0

Here is the answer for your case , and you can use len() to change the lengths of your lists.

nested_list= [[1, 3, 5], [3, 4, 5]]

sum_of_items_in_nested_list=[]
for j in range(0,3,1):
    result=0
    for i in range(0,2,1):
         result=result+nested_list[i][j]
         sum_of_items_in_nested_list = sum_of_items_in_nested_list + [result]

edited Oct 30, 2012 at 15:56

user447356

answered Oct 28, 2012 at 20:20

mzn.rft

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