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Sum 2D array in Python using map() function
  • Difficulty Level : Medium
  • Last Updated : 22 Nov, 2020

Given a 2-D matrix, we need to find sum of all elements present in matrix ?

Examples:

Input  : arr = [[1, 2, 3], 
                [4, 5, 6], 
                [2, 1, 2]]
Output : Sum = 26

This problem can be solved easily using two for loops by iterating whole matrix but we can solve this problem quickly in python using map() function.




# Function to calculate sum of all elements in matrix
# sum(arr) is a python inbuilt function which calculates
# sum of each element in a iterable ( array, list etc ).
# map(sum,arr) applies a given function to each item of 
# an iterable and returns a list of the results.
def findSum(arr):
  
    # inner map function applies inbuilt function  
    # sum on each row of matrix arr and returns 
    # list of sum of elements of each row
    return sum(map(sum,arr))  
  
# Driver function
if __name__ == "__main__":
    arr = [[1, 2, 3], [4, 5, 6], [2, 1, 2]]
    print ("Sum = ",findSum(arr))

Output:

26

What does map() do?
The map() function applies a given function to each item of an iterable(list, tuple etc.) and returns a list of the results. For example see given below example :






# Python code to demonstrate working of map()
  
# Function to calculate square of any number
def calculateSquare(n):
    return n*n
  
# numbers is a list of elements
numbers = [1, 2, 3, 4]
  
# Here map function is mapping calculateSquare 
# function to each element of numbers list.
# It is similar to pass each element of numbers 
# list one by one into calculateSquare function 
# and store result in another list
result = map(calculateSquare, numbers)
  
# resultant output will be [1,4,9,16]
print (result)

Output :

[1, 4, 9, 16]

This article is contributed by Shashank Mishra (Gullu). If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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