Transpose of a matrix using Python 3.8

Question

What is the transpose of a matrix:

In linear algebra, the transpose of a matrix is an operator which flips a matrix over its diagonal; that is, it switches the row and column indices of the matrix A by producing another matrix, often denoted by AT.

Code

dimension = int(input())
matrix = []
transpose = []
for row in range(dimension):
 entry = list(map(int,input().split()))
 matrix.append(entry)
for i in range(dimension):
 for j in range(dimension):
 transpose.append(matrix[j][i])
m = 0
n = dimension 
for x in range(dimension+1):
 
 row = transpose[m:n]
 list1 = [str(item) for item in row]
 string2 = " ".join(list1)
 print(string2)
 m = n
 n = n + dimension

My question

What all modifications I can do to this code to make it better furthermore efficient?

• superb rain: Example input and output would be useful.

Answer 1

You're converting the matrix elements to int and then back to string without doing anything with the ints, so that's just wasteful.

Anyway, the usual way to transpose is zip. Demo including mock input:

input = iter('''3
1 2 3
4 5 6
7 8 9'''.splitlines()).__next__
matrix = [input().split() for _ in range(int(input()))]
for column in zip(*matrix):
 print(*column)

Output:

1 4 7
2 5 8
3 6 9

Answer 2

You could do something like this:

dimension = int(input())
matrix = [list(map(int,input().split())) for _ in range(dimension)]
transpose = [[matrix[j][i] for j in range(dimension)] for i in range(dimension)]

PD: This still has to pass by every item on the matrix but it is a little more compact code, and if you're used to python you could find it a little more legible.

• pacmaninbw: Other than code is more compact is there a performance improvement, does the code run faster?
• Jorge Morgado: Practically this code does less iterations, 2n^2 where n is the dimension (yours do 3n^2) But in terms of algorithmic complexity this is still O(n^2).