colorful checkerboard-like matrix pattern

main.py

from typing import TypeVar
from collections.abc import Sequence
from sys import argv, stderr
from itertools import cycle, islice

T = TypeVar("T")

def dist(index: int, length: int) -> int:
    if not (0 <= index < length):
        raise ValueError("index must be in [0; length)")
    return min(index, length - index - 1)

def generate_matrix(size: int, alphabet: Sequence[T]) -> list[list[T]]:
    return [
        [
            alphabet[abs(dist(i, size) - dist(j, size))]
            for j in range(size)
        ]
        for i in range(size)
    ]


def main():
    try:
        size_arg = argv[1]
    except IndexError:
        size_arg = input("Enter the size: ")
    
    try: 
        size = int(size_arg)
    except ValueError:
        print("Invalid `size` argument", file=stderr)
        return
    
    alphabet = [f"\x1b[3{i+1}m{char} " for i, char in islice(cycle(enumerate("abcdefg")), size)]
    matrix = generate_matrix(size, alphabet)
    for row in matrix:
        print(*row, sep="", end="\x1b[m\n")

if __name__ == "__main__":
    main()