Question

How do i achieve line 9 and 10 i.e the two for loops in python

matrix = [
    [1, 2, 3, 4],
    [5, 6, 7, 8],
    [9, 10, 11, 12]
]

newMatrix = []

for (i=0; i < len(matrix); i++):
    for (j=0; j < len(matrix[i]); j++):
        newMatrix[j][i] = matrix[i][j]
print newMatrix

PS: i know i can do [[row[i] for row in matrix] for i in range(4)] but how i do only using for loops

Answer 1

Use range (or xrange).

for i in range(len(matrix)):
  for j in range(len(matrix[i])):

FYI, assigning to newMatrix[i][j] will fail, because newMatrix is an empty list. You need to add a new empty list to newMatrix for every row and then append the new value to that list in every iteration.