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Python: Sort a given matrix in ascending order according to the sum of its rows using lambda

Python Lambda: Exercise-30 with Solution

Write a Python program to sort a given matrix in ascending order according to the sum of its rows using lambda.

Sample Solution:

Python Code :

def sort_matrix(M):
    result = sorted(M, key=lambda matrix_row: sum(matrix_row)) 
    return result

matrix1 = [[1, 2, 3], [2, 4, 5], [1, 1, 1]]
matrix2 = [[1, 2, 3], [-2, 4, -5], [1, -1, 1]]

print("Original Matrix:")
print(matrix1)
print("\nSort the said matrix in ascending order according to the sum of its rows") 
print(sort_matrix(matrix1))
print("\nOriginal Matrix:")
print(matrix2) 
print("\nSort the said matrix in ascending order according to the sum of its rows") 
print(sort_matrix(matrix2))

Sample Output:

Original Matrix:
[[1, 2, 3], [2, 4, 5], [1, 1, 1]]

Sort the said matrix in ascending order according to the sum of its rows
[[1, 1, 1], [1, 2, 3], [2, 4, 5]]

Original Matrix:
[[1, 2, 3], [-2, 4, -5], [1, -1, 1]]

Sort the said matrix in ascending order according to the sum of its rows
[[-2, 4, -5], [1, -1, 1], [1, 2, 3]]

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Python: Tips of the Day

Find current directory and file's directory:

To get the full path to the directory a Python file is contained in, write this in that file:

import os 
dir_path = os.path.dirname(os.path.realpath(__file__))

(Note that the incantation above won't work if you've already used os.chdir() to change your current working directory, since the value of the __file__ constant is relative to the current working directory and is not changed by an os.chdir() call.)

To get the current working directory use

import os
cwd = os.getcwd()

Documentation references for the modules, constants and functions used above:

  • The os and os.path modules.
  • The __file__ constant
  • os.path.realpath(path) (returns "the canonical path of the specified filename, eliminating any symbolic links encountered in the path")
  • os.path.dirname(path) (returns "the directory name of pathname path")
  • os.getcwd() (returns "a string representing the current working directory")
  • os.chdir(path) ("change the current working directory to path")

Ref: https://bit.ly/3fy0R6m