# -*- coding: utf-8 -*
from abc import ABC,abstractclassmethod
from collections import namedtuple
Customer = namedtuple('Customer','name fidelity')
class LineItem:
def __init__(self,product,quantity,price):
self._product = product
self._quantity = quantity
self._price = price
def total(self):
return self._price * self._quantity
class Order: #上下文,也就是客户端代码
def __init__(self,customer,cart,promotion = None):
self._customer = customer
self._cart = list(cart)
self._promotion = promotion
def total(self):
if not hasattr(self, '__total'):
self.__total = sum(item.total() for item in self._cart)
return self.__total
def due(self):
"""折扣"""
if self._promotion is None:
discount = 0
else:
discount = self._promotion.discount(self)
return self.total() - discount
def __repr__(self):
fmt = '<Order total: {:.2f} due: {:.2f}>'
return fmt.format(self.total(), self.due())
class Promotion(ABC): #声明抽象基类的方法,继承abc.ABC(abstract base class)
@abstractclassmethod
def discount(self,order):
"""返回折扣金额(正值)"""
class FidelityPromo(Promotion): #第一个具体策略
"""为积分为1000或以上的顾客提供5%折扣"""
def discount(self,order):
return order.total() * 0.05 if order._customer.fidelity >= 1000 else 0
class BulkItemPromo(Promotion): # 第二个具体策略
"""单个商品为20个或以上时提供10%折扣"""
def discount(self, order):
discount = 0
for item in order._cart:
if item._quantity >= 20:
discount += item.total() * .1
return discount
class LargeOrderPromo(Promotion): # 第三个具体策略
"""订单中的不同商品达到10个或以上时提供7%折扣"""
def discount(self, order):
distinct_items = {item._product for item in order._cart}
if len(distinct_items) >= 10:
return order.total() * 0.07
return 0
if __name__ == '__main__':
joe = Customer('John Doe', 0) # 积分0
ann = Customer('Ann Smith',1100) #积分1100
cart = [LineItem('banana', 4, .5),LineItem('apple', 10, 1.5),LineItem('watermellon', 5, 5.0)] #3个商品的购物车
print(Order(joe,cart,FidelityPromo())) #<Order total: 42.00 due: 42.00>
print(Order(ann,cart,FidelityPromo())) #<Order total: 42.00 due: 39.90>
banana_cart = [LineItem('banana', 30, .5),LineItem('apple', 10, 1.5)]#30个香蕉和5个苹果
print(Order(joe,banana_cart,BulkItemPromo())) #<Order total: 30.00 due: 28.50>
long_order = [LineItem(str(item_code), 1, 1.0) for item_code in range(10)] #有 10 个不同的商品,每个商品的价格为 1.00 美元。
print(Order(joe,long_order,LargeOrderPromo())) #<Order total: 10.00 due: 9.30>
print(Order(joe, cart, LargeOrderPromo())) #<Order total: 42.00 due: 42.00>