Encrypt a text and concatenating the resultant text with itself by characters sorted

cipher_text.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Encrypt and Decrypt idea extracted from http://rodrigogr.com/blog/cifrado-de-transposicion/

import math

def main():
    text_encrypt = 'Guillermo Alfonso Morales, 1983-02-12, Santiago de Cali'
    key_length = int(len(text_encrypt) / 4)
    
    cipher_text = encrypt_text(key_length, text_encrypt)
    print(cipher_text)
    
    plain_text = decrypt_text(key_length, cipher_text)
    print(plain_text)


def encrypt_text(key, text):
    """ Encripts a text

    :param key: number of cols for the matriz
    :param text:
    :return:
    """
    # Columns at matriz
    cipher_text = [''] * key

    for col in range(key):
        pointer = col

        while pointer < len(text):
            # The character will be saved with 'key' plus in ascii value
            cipher_text[col] += chr(ord(text[pointer])+key)
            pointer += key

    # New lists with characters ordered ascending
    sorted_text = list(''.join(cipher_text))
    sorted_text.sort()

    # Concatenate both lists
    for i, v in enumerate(list(''.join(cipher_text))):
        sorted_text.insert(2 * i + 1, v)

    return ''.join(sorted_text)


def decrypt_text(key, text):
    """ Decrypts a matriz
    
    :param key: number of cols for the matriz
    :param text: Cipher Text to convert text
    :return:
    """
    # text only with the correct values
    text = [text[_] for _ in range(1, len(text), 2)]
    text = ''.join(text)
    # Number of columns and rows for the matriz
    num_columns = math.ceil(len(text) / key)
    num_rows = key
    # Empty cells quantity in the matriz
    num_empty_cells = (num_columns * num_rows) - len(text)
    plain_text = [''] * num_columns
    col = 0
    row = 0

    for symbol in text:
        plain_text[col] += chr(ord(symbol)-key)
        col += 1

        # If not cols or empty cell, then next row
        if (col == num_columns) or (col == num_columns - 1 and row >= num_rows - num_empty_cells):
            col = 0
            row += 1

    return ''.join(plain_text)
  
if __name__ == '__main__':
    main()