Matrix

def letters_to_ASCII(martix):
    """Analyse values in matrix and replace letters to ASCII code,
    creating an array of values which have been replaced.
    """
    values_to_replace = []
    for row in matrix:
        for value in row:
            if isinstance(value, str):
                row[row.index(value)] = ord(value)
                values_to_replace.append(ord(value))
    return matrix, values_to_replace


def get_matrix_params(matrix):
    """Function return matrix length and matrix values,
    sorted from min to max
    """
    matrix_length = len(matrix)
    matrix_values = []
    for row in matrix:
        for value in row:
            matrix_values.append(value)
    matrix_values.sort()
    return matrix_length, matrix_values


def create_new_matrix(matrix_length, matrix_values):
    """
    Create a new matrix with a diagonal with minimum values
    """
    minimal_diagonal = matrix_values[:matrix_length]
    other_values = matrix_values[matrix_length:]
    new_matrix = []
    while other_values:
        new_matrix.append(other_values[:matrix_length - 1])
        other_values = other_values[matrix_length - 1:]

    for i in range(matrix_length):
        new_matrix[i].insert(i, minimal_diagonal[i])
    return new_matrix


def ASCII_to_letters(new_martix, values_to_replace):
    """Analyse values in matrix and replace ASCII to letters
    in previously replaced values
    """
    for row in new_martix:
        for value in row:
            if value in values_to_replace:
                row[row.index(value)] = chr(value)
    return new_martix


if __name__ == '__main__':

    matrix = [[83, 255, -99, 711, 'w', 199],
              [670, 'Q', 134, 219, 164, 178],
              [135, 123, 330, 241, 177, 213],
              ['q', 169, 143, 154, 194, 126],
              [956, 459, 444, 122, 555, 453],
              [333, 677, 888, 832, 245, 228]]


    ASCII_matrix, values_to_replace = letters_to_ASCII(matrix)

    matrix_length, matrix_values = get_matrix_params(ASCII_matrix)

    new_matrix = create_new_matrix(matrix_length, matrix_values)

    result_matrix = ASCII_to_letters(new_matrix, values_to_replace)

    for row in result_matrix:
        print(row)