committed from zkp

pythonkd · pythonkd · commit dd5f2008381a · 2018-11-22T18:50:39.000+08:00
diff --git a/FluentPython/best_promos.py b/FluentPython/best_promos.py
@@ -0,0 +1,68 @@
+# from abc import ABC, abstractmethod
+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:
+
+    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):
+        if self.promotion is None:
+            discount = 0
+        else:
+            discount = self.promotion(self)
+        return self.total() - discount
+
+    def __repr__(self):
+        fmt = '<Order total: {:.2f} due: {:.2f}>'
+        return fmt.format(self.total(), self.due())
+
+
+def fidelity_promo(order):
+    '''为积分为1000或以上的顾客提供5%折扣'''
+    return order.total() * .05 if order.customer.fidelity >= 1000 else 0
+
+
+def bulkItem_promo(order):
+    '''单个商品为20个或以上时提供10%折扣'''
+    discount = 0
+    for item in order.cart:
+        if item.quantity >= 20:
+            discount += item.total() * .1
+    return discount
+
+
+def large_order_promo(order):
+    '''订单中的不同商品达到10个或以上时提供7%折扣'''
+    distinct_items = {item.product for item in order.cart}
+    if len(distinct_items) >= 10:
+        return order.total() * .07
+    return 0
+
+
+promos = [fidelity_promo, bulkItem_promo, large_order_promo]
+
+
+def best_promo(order):
+    '''选择可用的最佳折扣'''
+    return max(promo(order) for promo in promos)
