# Python – Matrix Transpose

## Python – Matrix Transpose

In Python, a Matrix can be represented using a nested list. Lists inside the list are the rows.

Following is a simple example of nested list which could be considered as a `2x3` matrix.

``matrixA = [ [2, 8, 4], [3, 1, 5] ]``
Run

The two lists inside `matrixA` are the rows of the matrix. Number of elements inside a row represent the number of columns.

Also, in Python programming, the indexing start from `0`. So, when we specify `matrixA` in the program, that is actually `[2+1][4+1] = `, element of third row and fifth column.

In this tutorial, we will learn how to Transpose a Matrix in Python.

### Example 1: Python Matrix Transpose using List Comprehension

In this example, we shall take a Matrix defined using Python List, and find its Transpose using List Comprehension.

Python Program

``````A = [ [2, 1, 3], [3, 1, 5] ]

#transpose of A
B = [[A[j][i] for j in range(len(A))] for i in range(len(A))]

print(' A:', A)
print(' B:', B)``````
Run

The code for addition of matrices using List Comprehension is very concise.

Output

`````` A: [[2, 1, 3], [3, 1, 5]]
B: [[2, 3], [1, 1], [3, 5]]``````

### Example 2: Python Matrix Transpose using For Loop

In this example, we shall take a matrix, represented using Python List and find its transpose by traversing through the elements using for Loop.

Python Program

``````A = [ [2, 1, 3], [3, 1, 5] ]

#initialize B with size of A transpose
B = [[0 for j in range(len(A))] for i in range(len(A))]

for j in range(len(A)):
for i in range(len(A)):
B[i][j] = A[j][i]

print(' A:', A)
print(' B:', B)``````
Run

Output

`````` A: [[2, 1, 3], [3, 1, 5]]
B: [[2, 3], [1, 1], [3, 5]]``````

This method is only for demonstrating the transpose of a matrix using for loop. List comprehension used in the first example is preferred, as it is concise.

### Summary

In this tutorial of Python Examples, we learned how to do Matrix Transpose in Python using For loop and List comprehension, with the help of well detailed examples.