incorrect output when trying to rotate a matrix in python -

i'm trying rotate matrix(2-d list) in python 90 degrees clockwise. here code:

def rotate(matrix):      length = len(matrix)      new_matrix = [[0]*length]*length      in range(length):          j in range(length):              new_matrix[j][length-1-i] = matrix[i][j]              print("new_matrix[",j,"][", length-1-i,"]", "is", new_matrix[j][length-1-i])      in range(length):          j in range(length):              print(new_matrix[i][j])      return new_matrix print(rotate([[1 ,2], [3, 4]])) 

the idea simple, after rotating, element i, j row number , column number have j, length-1-i row , column numbers.

the print statement used verify doing right. tried [[1, 2], [3, 4]] , got wrong answer , quite confusing output:

new_matrix[ 0 ][ 1 ] 1 new_matrix[ 1 ][ 1 ] 2 new_matrix[ 0 ][ 0 ] 3 new_matrix[ 1 ][ 0 ] 4 4 2 4 2 [[4, 2], [4, 2]] 

it seems somehow values 1 , 3 got overwritten somehow. , when tried [[1, 2, 3], [4, 5, 6], [7, 8, 8]] , new_matrix became [[9, 6, 3], [9, 6, 3], [9, 6, 3]]. there wrong here.

any idea why?

the problem in code line,

new_matrix = [[0]*length]*length 

it's not doing think - creating list of length number of same inner list.

replace following create distinct inner lists,

new_matrix = [[0]*length _ in range(length)]