Python | Column wise sum of nested list
Given a nested list (where sublists are of equal length), write a Python program to find the column-wise sum of the given list and return it in a new list.
Examples:
Input : [[1, 5, 3],
[2, 7, 8],
[4, 6, 9]]
Output : [7, 18, 20]
Input : [[20, 5],
[2, 54],
[45, 9],
[72, 3]]
Output : [139, 71]
Method #1 : zip using list comprehension
We can find sum of each column of the given nested list using zip function of python enclosing it within list comprehension.
# Python3 program to Column wise sum of nested list def column_sum(lst): return [sum(i) for i in zip(*lst)] # Driver code lst = [[1, 5, 3], [2, 7, 8], [4, 6, 9]] print(column_sum(lst)) |
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Output:
[7, 18, 20]
Method #2 : Using map() method
Another apporach is to use map(). We apply the sum function to each element in a column and find sum of each column accordingly.
# Python3 program to Column wise sum of nested list def column_sum(lst): return list(map(sum, zip(*lst))) # Driver code lst = [[1, 5, 3], [2, 7, 8], [4, 6, 9]] print(column_sum(lst)) |
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Output:
[7, 18, 20]
Method #3 : Using numpy.sum()
numpy.sum() function returns the sum of array elements over the specified axis.
# Python3 program to Column wise sum of nested list from numpy import array def column_sum(lst): arr = array(lst) return sum(arr, 0).tolist() # Driver code lst = [[1, 5, 3], [2, 7, 8], [4, 6, 9]] print(column_sum(lst)) |
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Output:
[7, 18, 20]
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