一站式教学练平台优惠卷

class Coupon:
    def __init__(self, code, discount, expiration_date):
        self.code = code
        self.discount = discount
        self.expiration_date = expiration_date

    def is_valid(self, current_date):
        return current_date <= self.expiration_date

def apply_coupon(coupon, order_total):
    if coupon.is_valid(datetime.now()):
        return order_total * (1 - coupon.discount)
    else:
        raise ValueError("Coupon has expired.")

# 使用示例
coupon = Coupon(code="SAVE20", discount=0.2, expiration_date=datetime(2023, 12, 31))
try:
    new_total = apply_coupon(coupon, 100)
    print(f"New total after coupon: {new_total}")
except ValueError as e:
    print(e)