Flipping a matrix-like string horizontally

The goal of this function is to flip a matrix-like string horizontally.

For example the string: '100010001' with 2 rows and three columns would look like:

1 0 0
0 1 0
0 0 1

but when flipped should look like:

0 0 1
0 1 0
1 0 0

So the function would return the following output: '001010100'

The caveat, I cannot use lists or arrays. only strings.

The current code I have written up, I believe, should work, however it is returning an empty string.

def flip_horizontal(image, rows, column):

   horizontal_image = ''
   for i in range(rows):

       #This should slice the image string, and map image(the last element in the 
       #column : to the first element of the column) onto horizontal_image.
       #this will repeat for the given amount of rows

       horizontal_image = horizontal_image + image[(i+1)*column-1:i*column]
    
   return horizontal_image

Again this returns an empty string. Any clue what the issue is?

Solution

The range function can be used to isolate your string into steps that represent rows. While iterating through the string you can use [::-1] to reverse each row to achieve the horizontal flip.

string = '100010001'
output = ''
prev = 0

# Iterate through string in steps of 3
for i in range(3, len(string) + 1, 3):

  # Isolate and reverse row of string
  row = string[prev:i]
  row = row[::-1]

  output = output + row
  prev = i

Input:

'100
 010
 001'

Output:

'001
 010
 100'