ShopBot/keyboard/inline/checkout.py

from aiogram.types.inline_keyboard import InlineKeyboardMarkup, InlineKeyboardButton


def cart_list(item: int = 0, items: int = 1) -> InlineKeyboardMarkup:
    markup = InlineKeyboardMarkup()
    default = [
        InlineKeyboardButton(str(item+1), callback_data='null')
    ]
    back = ['⬅️', f"cart_prev|{item-1}"]
    next = ['➡️', f"cart_next|{item+1}"]

    if items < 1 or item >= items:
        next = [" ", "null"]
    
    if item <= 0:
        back = [" ", "null"]

    default.append(InlineKeyboardButton(next[0], callback_data=next[1]))

    markup.add(InlineKeyboardButton(back[0], callback_data=back[1]), *default)
    return markup