import re
def quantity(value):
    if not isinstance(value, str) or not re.fullmatch(r"[0-9]{1,2}", value):
        raise ValueError("quantity format")
    number = int(value)
    if not 1 <= number <= 12:
        raise ValueError("quantity range")
    return number
assert quantity("3") == 3
for bad in ["0", "13", "-1", "3.0", "", "１２", None]:
    try:
        quantity(bad)
    except ValueError:
        continue
    raise AssertionError(bad)
print("valid quantity accepted; seven invalid inputs rejected")