two.py

from functools import cmp_to_key

def parse(text):
    list_stack = []
    current_list = None
    current_number = []
    for c in text:
        match c:
            case "[":
                if current_list is None:
                    current_list = list()
                else:
                    list_stack.append(current_list)
                    current_list.append(list())
                    current_list = current_list[-1]
            case "]":
                if current_number:
                    current_list.append(int("".join(current_number)))
                    current_number = []
                if list_stack:
                    current_list = list_stack.pop()
            case ",":
                if current_number:
                    current_list.append(int("".join(current_number)))
                    current_number = []
            case _:
                current_number.append(c)
    return current_list


def singles(filename):
    with open(filename) as fileh:
        for line in fileh:
            if line.strip():
                yield parse(line.strip())


def compare(a, b):
    if isinstance(a, int) and isinstance(b, int):
        if a < b:
            return 1
        elif a > b:
            return -1
        else:
            return 0
    if isinstance(a, int):
        a = [a]
    if isinstance(b, int):
        b = [b]
    for i in range(len(a)):
        if i >= len(b):
            return -1
        c = compare(a[i], b[i])
        if c != 0:
            return c
    if len(a) == len(b):
        return 0
    return 1

def main(filename):
    signals = sorted([[[2]], [[6]]] + list(singles(filename)), key=cmp_to_key(compare), reverse=True)
    # print("\n".join(str(signal) for signal in signals))
    for i, signal in enumerate(signals, start=1):
        if signal == [[6]]:
            a = i
        if signal == [[2]]:
            b = i
    return a * b

if __name__ == "__main__":
    print(main("example"))
    print(main("input"))