企业搜索优惠卷

class CouponTracker:
    def __init__(self, coupon_code, discount_rate, expiration_date):
        self.coupon_code = coupon_code
        self.discount_rate = discount_rate
        self.expiration_date = expiration_date
        self.used = False

    def apply_discount(self, amount):
        if not self.used and datetime.now() < self.expiration_date:
            discount_amount = amount * self.discount_rate
            self.used = True
            return amount - discount_amount
        else:
            raise ValueError("Coupon has expired or already used.")

# 使用示例
tracker = CouponTracker('SAVE20', 0.2, datetime(2023, 12, 31))
try:
    final_price = tracker.apply_discount(100)
    print(f"Final price after discount: {final_price}")
except ValueError as e:
    print(e)