In the previous article, we have discussed Python Program for Squares of Matrix Diagonal Elements

Given a matrix, the task is to interchange the elements of the first and the last rows of a given matrix.

**What is a matrix:**

A matrix is a rectangular sequence of numbers divided into columns and rows. A matrix element or entry is a number that appears in a matrix.

**Example:**

Above is the matrix which contains 5 rows and 4 columns and having elements from 1 to 20.

In this order, the dimensions of a matrix indicate the number of rows and columns.

**Examples:**

**Example1:**

**Input:**

Given Matrix : 2 3 4 1 7 45 8 2 3

**Output:**

The given matix after swapping the first and last row elements: 8 2 3 1 7 45 2 3 4

**Example2:**

**Input:**

Given Matrix : 1 2 3 4 5 6 7 8 9

**Output:**

The given matix after swapping the first and last row elements: 7 8 9 4 5 6 1 2 3

## Program to Interchange Elements of First and Last Rows in Matrix in Python

Below are the ways to interchange the elements of the first and the last rows of a given matrix in python:

### Method #1: Using For Loop (Static Input)

**Approach:**

- Give the matrix as static input and store it in a variable.
- Calculate the number of rows of the given matrix by calculating the length of the nested list using the len() function and store it in a variable mtrxrows.
- Calculate the number of columns of the given matrix by calculating the length of the first list in the nested list using the len() function and store it in a variable mtrxcolums.
- Loop till the given number of rows using the For loop.
- Inside the For loop, swap mtrx[0][itr], mtrx[mtrxrows-1][itr] using the comma(,) operator ( where itr is the iterator value and mtrxrows is the no of rows of matrix).
- To print all the elements of the given matrix.
- Loop till the given number of rows using the For loop.
- Inside the For loop, Iterate till the given number of rows using another Nested For loop(Inner For loop).
- Print the element of the matrix by printing
**gvnmatrix[n][m]**value where n is the iterator value of the parent For loop and m is the iterator value of the inner For loop. - The Exit of the Program.

**Below is the implementation:**

# Give the matrix as static input and store it in a variable. mtrx = [[1, 2, 3], [4, 5, 6], [7, 8, 9]] # Calculate the number of rows of the given matrix by # calculating the length of the nested list using the len() function # and store it in a variable mtrxrows. mtrxrows = len(mtrx) # Calculate the number of columns of the given matrix by # calculating the length of the first list in the nested list # using the len() function and store it in a variable mtrxcols. mtrxcols = len(mtrx[0]) print("The given matix after swapping the first and last row elements: ") # Loop till the given number of rows using the For loop. for itr in range(mtrxrows): # Inside the For loop, swap mtrx[0][itr], mtrx[mtrxrows-1][itr] using the comma(,) operator # ( where itr is the iterator value and mtrxrows is the no of rows of matrix). mtrx[0][itr], mtrx[mtrxrows-1][itr] = mtrx[mtrxrows-1][itr], mtrx[0][itr] # Loop till the given number of rows using the For loop. for n in range(mtrxrows): # Inside the For loop, Iterate till the given number of rows using another # Nested For loop(Inner For loop). for m in range(mtrxcols): # Print the element of the matrix by printing gvnmatrix[n][m] value # where n is the iterator value of the parent For loop and m is the iterator # value of the inner For loop. print(mtrx[n][m], end=' ') print()

**Output:**

The given matix after swapping the first and last row elements: 7 8 9 4 5 6 1 2 3

### Method #2: Using For loop (User Input)

**Approach:**

- Give the number of rows of the matrix as user input using the int(input()) function and store it in a variable.
- Give the number of columns of the matrix as user input using the int(input()) function and store it in another variable.
- Take a list and initialize it with an empty value using [] or list() to say
**gvnmatrix**. - Loop till the given number of rows using the For loop
- Inside the For loop, Give all the row elements of the given Matrix as a list using the list(),map(),int(),split() functions and store it in a variable.
- Add the above row elements list to
**gvnmatrix**using the append() function. - Loop till the given number of rows using the For loop.
- Inside the For loop, swap mtrx[0][itr], mtrx[mtrxrows-1][itr] using the comma(,) operator ( where itr is the iterator value and mtrxrows is the no of rows of matrix).
- To print all the elements of the given matrix.
- Loop till the given number of rows using the For loop.
- Inside the For loop, Iterate till the given number of rows using another Nested For loop(Inner For loop).
- Print the element of the matrix by printing
**gvnmatrix[n][m]**value where n is the iterator value of the parent For loop and m is the iterator value of the inner For loop. - The Exit of the Program.

**Below is the implementation:**

# Give the number of rows of the matrix as user input using the int(input()) function # and store it in a variable. mtrxrows = int(input('Enter some random number of rows of the matrix = ')) # Give the number of columns of the matrix as user input using the int(input()) function # and store it in another variable. mtrxcols = int(input('Enter some random number of columns of the matrix = ')) # Take a list and initialize it with an empty value using [] or list() to say gvnmatrix. mtrx = [] # Loop till the given number of rows using the For loop for n in range(mtrxrows): # Inside the For loop, Give all the row elements of the given Matrix as a list using # the list(),map(),int(),split() functions and store it in a variable. l = list(map(int, input( 'Enter {'+str(mtrxcols)+'} elements of row {'+str(n+1)+'} separated by spaces = ').split())) # Add the above row elements list to gvnmatrix using the append() function. mtrx.append(l) print("The given matix after swapping the first and last row elements: ") # Loop till the given number of rows using the For loop. for itr in range(mtrxrows): # Inside the For loop, swap mtrx[0][itr], mtrx[mtrxrows-1][itr] using the comma(,) operator # ( where itr is the iterator value and mtrxrows is the no of rows of matrix). mtrx[0][itr], mtrx[mtrxrows-1][itr] = mtrx[mtrxrows-1][itr], mtrx[0][itr] # Loop till the given number of rows using the For loop. for n in range(mtrxrows): # Inside the For loop, Iterate till the given number of rows using another # Nested For loop(Inner For loop). for m in range(mtrxcols): # Print the element of the matrix by printing gvnmatrix[n][m] value # where n is the iterator value of the parent For loop and m is the iterator # value of the inner For loop. print(mtrx[n][m], end=' ') print()

**Output:**

Enter some random number of rows of the matrix = 3 Enter some random number of columns of the matrix = 3 Enter {3} elements of row {1} separated by spaces = 2 3 4 Enter {3} elements of row {2} separated by spaces = 1 7 45 Enter {3} elements of row {3} separated by spaces = 8 2 3 The given matix after swapping the first and last row elements: 8 2 3 1 7 45 2 3 4

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