ch08, 09, 10: example files

10-dp-1class-func/strategy_best.py

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+# strategy_best.py
+# Strategy pattern -- function-based implementation
+# selecting best promotion from static list of functions
+
+"""
+    >>> joe = Customer('John Doe', 0)
+    >>> ann = Customer('Ann Smith', 1100)
+    >>> cart = [LineItem('banana', 4, .5),
+    ...         LineItem('apple', 10, 1.5),
+    ...         LineItem('watermellon', 5, 5.0)]
+    >>> banana_cart = [LineItem('banana', 30, .5),
+    ...                LineItem('apple', 10, 1.5)]
+    >>> big_cart = [LineItem(str(item_code), 1, 1.0)
+    ...               for item_code in range(10)]
+
+# tag::STRATEGY_BEST_TESTS[]
+
+    >>> Order(joe, big_cart, best_promo)  # <1>
+    <Order total: 10.00 due: 9.30>
+    >>> Order(joe, banana_cart, best_promo)  # <2>
+    <Order total: 30.00 due: 28.50>
+    >>> Order(ann, cart, best_promo)  # <3>
+    <Order total: 42.00 due: 39.90>
+
+# end::STRATEGY_BEST_TESTS[]
+"""
+
+from strategy import Customer, LineItem, Order
+from strategy import fidelity_promo, bulk_item_promo, large_order_promo
+
+# tag::STRATEGY_BEST[]
+
+promos = [fidelity_promo, bulk_item_promo, large_order_promo]  # <1>
+
+
+def best_promo(order) -> float:  # <2>
+    """Select best discount available
+    """
+    return max(promo(order) for promo in promos)  # <3>
+
+
+# end::STRATEGY_BEST[]