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Summing a 2D array in Python using the map () function

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Examples:

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

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

# A function to calculate the sum of all elements in a matrix
# sum (arr) is a built-in Python function that calculates
# the sum of each item in the iterable (array, list, etc.).
# map (sum, arr) applies the given function to each item
# iterable and returns a list of results.

def findSum (arr):

 

# internal map function applies inline function

# sum on each line arr matrices 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 the given function to each element of the iterable (list , tuple, etc.) and returns a list of results. For example, see the example below:

# Python code to demonstrate how map () works

 
# Function for calculating the square of any number

def calculateSquare (n):

return n * n

 
# numbers is a list of elements

numbers = [ 1 , 2 , 3 , 4 ]

 
# Here the map function displays
Function # for each item in the list of numbers.
# It’s like skipping each element of numbers
# listing one by one into the calcSquare function
# and save the result in another list

result = map (calculateSquare, numbers)

 
# the resulting output will be [1,4,9,16]

print result

Output:

 [1 , 4, 9, 16] 

This article courtesy of Shashankom Mishra (Gullu) . If you are as Python.Engineering and would like to contribute, you can also write an article using contribute.python.engineering or by posting an article contribute @ python.engineering. See my article appearing on the Python.Engineering homepage and help other geeks.

Please post comments if you find anything wrong or if you’d like to share more information on the topic discussed above.

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