Skip to content
Related Articles

Related Articles

Improve Article
Python – Summation Matrix columns
  • Last Updated : 30 Dec, 2020

Sometimes, we are encountered with such problem in which we need to find the sum of each column in a matrix i.e sum of each index in list of lists. This kind of problem is quite common and useful in competitive programming. Let’s discuss certain ways in which this problem can be solved.

Method #1 : Using sum() + list comprehension + zip()
The combination of above methods are required to solve this particular problem. The sum function is used to get the required sum value and zip function provides the combination of like indices and then list is created using list comprehension.




# Python3 code to demonstrate
# Summation of each column in Matrix
# using sum() + list comprehension + zip()
  
# initializing list
test_list = [[3, 7, 6], [1, 3, 5], [9, 3, 2]]
  
# printing original list
print("The original list : " + str(test_list))
  
# using sum() + list comprehension + zip()
# Summation of each column in Matrix
res = [sum(idx) for idx in zip(*test_list)]
  
# print result
print("The Summation of each index list is : " + str(res))
Output :
The original list : [[3, 7, 6], [1, 3, 5], [9, 3, 2]]
The Summation of each index list is : [13, 13, 13]

 

Method #2 : Using map() + sum() + zip()
This works in almost similar way as the above method, but the difference is just that we use map function to build the sum list rather than using list comprehension.






# Python3 code to demonstrate
# Summation of each column in Matrix
# using map() + sum() + zip()
  
# initializing list
test_list = [[3, 7, 6], [1, 3, 5], [9, 3, 2]]
  
# printing original list
print("The original list : " + str(test_list))
  
# using map() + sum() + zip()
# Summation of each column in Matrix
res = list(map(sum, zip(*test_list)))
  
# print result
print("The Summation of each index list is : " + str(res))
Output :
The original list : [[3, 7, 6], [1, 3, 5], [9, 3, 2]]
The Summation of each index list is : [13, 13, 13]

 Attention geek! Strengthen your foundations with the Python Programming Foundation Course and learn the basics.  

To begin with, your interview preparations Enhance your Data Structures concepts with the Python DS Course. And to begin with your Machine Learning Journey, join the Machine Learning – Basic Level Course




My Personal Notes arrow_drop_up
Recommended Articles
Page :