Python program implementation of matrix transpose

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In this example, you will learn about matrix transpose (by using nested lists to create a matrix).

To understand this example, you should understand the followingPython programmingTopic:

• Python for loop

• Python list

In Python, we can implement a matrix as a nested list (a list of lists). We can consider each element as a row of the matrix.

For example, X = [[1, 2], [4, 5], [3, 6]] will represent a3x2matrix. The first row can be chosen as X[0]. And, the element in the first row and first column can be chosen as X[0][0].

The transpose of a matrix is the interchange of rows and columns. It is represented as X'. The element in the i-th row and j-th column of X will be placed in the j-th row and i-th column of X'. Therefore, if X is3x2matrix, then X' will be2x3matrix.

There are several ways to perform this operation in Python.

Matrix transpose using nested loops

# Program uses nested loops to transpose a matrix
X = [[12,7],
　　　　[4　,5],
　　　　[3　,8]]
result = [[0,0,0],
　　　　　　　　　[0,0,0]]
# iterate through rows
for i in range(len(X)):
　　　# iterate through columns
　　　for j in range(len(X[0])):
　　　　　　　result[j][i] = X[i][j]
for r in result:
　　　print(r)

Output result

[12,　4,　3]
[7,　5,　8]

In this program, we use nested for loops to iterate through each row and column. At each point, we place the X[i][j] element in result[j][i].

Matrix transpose using nested list comprehension

''' Program uses list comprehension to transpose a matrix '''
X = [[12,7],
　　　　[4　,5],
　　　　[3　,8]]
result = [[X[j][i] for j in range(len(X))] for i in range(len(X[0]))]
for r in result:
　　　print(r)

The output of this program is the same as the one above. We use nested list comprehensions to iterate through each element in the matrix.

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