Python – Summation of kth column in a matrix

Sometimes, while working with Python Matrix, we may have a problem in which we require to find the summation of a particular column. This can have a possible application in day-day programming and competitive programming. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using sum() + zip()
This task can be solved using the combination of above functions. In this, we pass in the zip() the list, to access all columns and sum() to get summation of columns.

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# Python3 code to demonstrate working of
# Matrix Kth column summation
# using sum() + zip()
  
# initialize list
test_list = [[5, 6, 7],
            [9, 10, 2], 
            [10, 3, 4]]
  
# printing original list
print("The original list is : " + str(test_list))
  
# initialize K
K = 2
  
# Matrix Kth column summation
# using sum() + zip()
res = [sum(idx) for idx in zip(*test_list)][K] 
  
# printing result
print("Sum of Kth column is : " + str(res))

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Output :

The original list is : [[5, 6, 7], [9, 10, 2], [10, 3, 4]]
Sum of Kth column is : 13

 

Method #2 : Using loop
This is brute force way to solve this problem. In this, we iterate through the matrix and take summation of column by testing column number.

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# Python3 code to demonstrate working of
# Matrix Kth column summation
# Using loop
  
# initialize list
test_list = [[5, 6, 7],
            [9, 10, 2], 
            [10, 3, 4]]
  
# printing original list
print("The original list is : " + str(test_list))
  
# initialize K
K = 2
  
# Matrix Kth column summation
# Using loop
res = 0
for sub in test_list:
    for idx in range(0, len(sub)):
        if idx == K:
            res = res + sub[idx]
  
# printing result
print("Sum of Kth column is : " + str(res))

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Output :

The original list is : [[5, 6, 7], [9, 10, 2], [10, 3, 4]]
Sum of Kth column is : 13



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