from random import randint

@register.assignment_tag()
def random_number(length=3):
    """
    Create a random integer with given length.
    For a length of 3 it will be between 100 and 999.
    For a length of 4 it will be between 1000 and 9999.
    """
    return randint(10**(length-1), (10**(length)-1))