ch06: update from book draft

06-obj-ref/cheese.py

@@ -0,0 +1,28 @@
+"""
+>>> import weakref
+>>> stock = weakref.WeakValueDictionary()
+>>> catalog = [Cheese('Red Leicester'), Cheese('Tilsit'),
+...                 Cheese('Brie'), Cheese('Parmesan')]
+...
+>>> for cheese in catalog:
+...     stock[cheese.kind] = cheese
+...
+>>> sorted(stock.keys())
+['Brie', 'Parmesan', 'Red Leicester', 'Tilsit']
+>>> del catalog
+>>> sorted(stock.keys())
+['Parmesan']
+>>> del cheese
+>>> sorted(stock.keys())
+[]
+"""
+
+# tag::CHEESE_CLASS[]
+class Cheese:
+
+    def __init__(self, kind):
+        self.kind = kind
+
+    def __repr__(self):
+        return 'Cheese(%r)' % self.kind
+# end::CHEESE_CLASS[]