##### Summing up rows and columns
 Summing up rows and columns plumberpy Silly Frenchman Posts: 32 Threads: 11 Joined: Aug 2021 Reputation: Aug-13-2021, 06:16 AM (This post was last modified: Aug-13-2021, 06:16 AM by plumberpy.) ```result = [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16]] qq = sum(result[3])```A. I can sum up all the rows using sum(). But how to sum the columns? Beside using the long method result[0][0]+result[1][0]+result[2][0]+result[3][0]. B. sum() will not work if one of the list elements is blank. Any way to resolve this? Many thanks. P/S Found the answers. I should try harder n my search! Ha. https://www.geeksforgeeks.org/python-col...sted-list/ Reply Posts: 1,951 Threads: 34 Joined: Sep 2016 Reputation: Aug-13-2021, 06:19 AM You could transpose the rows into columns and then use sum ```from itertools import zip_longest rows = [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16]] print(rows) def transpose_rows(rows): return tuple(zip_longest(*rows, fillvalue=0)) columns = transpose_rows(rows) print(columns) print(sum(columns[3]))`````````Output:[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16]] ((1, 5, 9, 13), (2, 6, 10, 14), (3, 7, 11, 15), (4, 8, 12, 16)) 40`````` Reply plumberpy Silly Frenchman Posts: 32 Threads: 11 Joined: Aug 2021 Reputation: Aug-13-2021, 12:37 PM (Aug-13-2021, 06:19 AM)Yoriz Wrote: You could transpose the rows into columns and then use sum ```from itertools import zip_longest rows = [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16]] print(rows) def transpose_rows(rows): return tuple(zip_longest(*rows, fillvalue=0)) columns = transpose_rows(rows) print(columns) print(sum(columns[3]))`````````Output:[[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16]] ((1, 5, 9, 13), (2, 6, 10, 14), (3, 7, 11, 15), (4, 8, 12, 16)) 40``````Noted. Good idea! Reply naughtyCat Silly Frenchman Posts: 45 Threads: 0 Joined: Aug 2021 Reputation: Aug-18-2021, 05:46 AM ```arr1 = [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16]] arr2 = [list(col) for col in zip(*arr1)] print(arr2) print(sum(arr2[3]))`````````Output:[[1, 5, 9, 13], [2, 6, 10, 14], [3, 7, 11, 15], [4, 8, 12, 16]] 40`````` Reply

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