Not receiving a number after the command, should the bot send a message?

Question

Python

When someone writes to the bot: "/number 5" the bot replies: "Your number is 5" But if someone writes "/number" then an error pops up because there is no number. How to make the bot write in such a situation: "Enter a number"

@dp.message_handler(commands=['number'])
async def number(message: types.Message):
    number = message.get_args()
    number1 = int(number)*1000
    if int(number) < 0:
        await message.reply("Нельзя вводить отрицательное число")
    else:
        await message.reply(f"Твое число {number1}")

Answer 1

I suspect that number is set to None so that it can be tied to.
Try this, it might work

@dp.message_handler(commands=['number'])
async def number(message: types.Message):
    number = message.get_args()
    if number is None:
        await message.reply(f"Твое число {number}")
    else:
        await message.reply("Введите число")

Answer 2

Based on your

code

@dp.message_handler(commands=['number'])
async def number(message: types.Message):
    number = message.get_args()
    number1 = int(number)*1000
    if int(number) < 0:
        await message.reply("Нельзя вводить отрицательное число")
    else:
        await message.reply(f"Твое число {number1}")

which you wrote in a comment to the answer above.
You should check if there is a deeplink and if it is a number

for example

@dp.message_handler(commands=['number'])
async def number(message: types.Message):
    number = message.get_args()
    if number is not None and number.isdigit():
        if int(number) < 0:
            await message.reply("Нельзя вводить отрицательное число")
        else:
            await message.reply(f"Твое число {int(number) * 1000}")
    elif number is None:
        await message.reply(f'Введите число после команды "/number 5 "')
    else:
        await message.reply(f'После команды "/number" ожидается число, а не текст')