How to sum two rows in a list?

Question

I want to sum the 3rd and 4th rows in my list? I am looking for the easiest way to do that? I know it seems so easy, but I cannot find the similar examples, as I am thinking I don't use the right keywords!

[0.001, 0.017000000000000001, 4.0, 75.0]
[5352984.0, 23194715.0, 8.0, 150.0]
[2370914.0, 11533745.0, 21.0, 396.0]
[0.39500000000000002, 0.68100000000000005, 68.0, 1296.0]
[0.46400000000000002, 0.69099999999999995, 69.0, 1307.0]
[0.0, 0.001, 12.0, 226.0]
[0.0, 0.001, 10.0, 194.0]
[0.055, 0.22600000000000001, 7.0, 136.0]
[0.055, 0.109, 10.0, 181.0]
[0.001, 0.037999999999999999, 29.0, 556.0]
[0.0030000000000000001, 0.14099999999999999, 46.0, 873.0]
[0.0, 1.0, 15.0, 287.0]
[0.0, 0.0, 6.0, 108.0]
[0.0, 0.0, 29.0, 556.0]
[0.0, 0.024, 46.0, 873.0]
[7086684.0, 68448914.0, 3.0, 53.0]

This is an improper example and shows no effort. If you cant code it, explain with some sample data as to what is going on and what you want to occur. — Fallenreaper, Jul 24 '19 at 22:58
If you update the question with the expected output and your current code that tries to implement this feature, we can try to answer your question. — PyNoob, Jul 24 '19 at 23:01
What is the value of `row`? Isn't it as simple as `row[0] + row[1]`? — Paul Rooney, Jul 24 '19 at 23:01
I just modified the question and the items in the rows I have — Nazanin Shambayati, Jul 24 '19 at 23:07
If it's always those same rows, you could do `[x + y for x,y in zip(a[2], a[3])]`. — PyNoob, Jul 24 '19 at 23:08
Possible duplicate of [Element-wise addition of 2 lists?](https://stackoverflow.com/questions/18713321/element-wise-addition-of-2-lists) — PyNoob, Jul 24 '19 at 23:09
Note that [SO](https://stackoverflow.com) isn't a code writing service. Please post what you've tried so far, and where did you encounter problems. Check [\[SO\]: How do I ask a good question?](https://stackoverflow.com/help/how-to-ask) or [\[SO\]: How to create a Minimal, Complete, and Verifiable example (mcve)](https://stackoverflow.com/help/mcve) for more asking related details. — CristiFati, Jul 24 '19 at 23:21

score 1 · Answer 1 · edited Jul 25 '19 at 01:18

Supposing that your list is like this:

this_list = [[0.001, 0.017000000000000001, 4.0, 75.0],
             [5352984.0, 23194715.0, 8.0, 150.0],
             [2370914.0, 11533745.0, 21.0, 396.0],
             [0.39500000000000002, 0.68100000000000005, 68.0, 1296.0],
             [0.46400000000000002, 0.69099999999999995, 69.0, 1307.0],
             [0.0, 0.001, 12.0, 226.0],
             [0.0, 0.001, 10.0, 194.0],
             [0.055, 0.22600000000000001, 7.0, 136.0],
             [0.055, 0.109, 10.0, 181.0],
             [0.001, 0.037999999999999999, 29.0, 556.0],
             [0.0030000000000000001, 0.14099999999999999, 46.0, 873.0],
             [0.0, 1.0, 15.0, 287.0],
             [0.0, 0.0, 6.0, 108.0],
             [0.0, 0.0, 29.0, 556.0],
             [0.0, 0.024, 46.0, 873.0],
             [7086684.0, 68448914.0, 3.0, 53.0]]

and your "3rd row" is this:

[ 4.,  8., 21., 68., 69., 12., 10.,  7., 10., 29., 46., 15.,  6., 29., 46.,  3.]

Then you can simply:

import numpy as np
np_list = np.array(this_list)
# sum in a new row
new_row = np.sum([np_list[:,2], np_list[:,3]], axis=0)

# sum each elements of the 3rd and 4rd rows separetadly
row3, row4 = np.sum([np_list[:,2], np_list[:,3]], axis=1)

score 0 · Answer 2 · 2019-07-30T14:22:15.130

A function can be made for this.

def RowSum (gridlist,row):
        sumcount=0
        for sublist in gridlist: # iterates through every sublist
                   sumcount+=sublist[row-1]
        return sumcount

For your work of summation of row 3 and 4:

rsum= RowSum(gridlist,3)+RowSum(gridlist,4)
print(rsum)

Note that this function is designed keeping in mind that the row number starts from 1 and not from 0.

Thank You :)

How to sum two rows in a list?

2 Answers2