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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.

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