updates to ch.14

14-inheritance/diamond.py

@@ -1,27 +1,62 @@
-class A:
+"""
+diamond1.py: Demo of diamond-shaped class graph.
+
+# tag::LEAF_MRO[]
+>>> Leaf.__mro__  # doctest:+NORMALIZE_WHITESPACE
+    (<class 'diamond1.Leaf'>, <class 'diamond1.A'>, <class 'diamond1.B'>,
+     <class 'diamond1.Root'>, <class 'object'>)
+
+# end::LEAF_MRO[]
+
+# tag::DIAMOND_CALLS[]
+    >>> leaf1 = Leaf()  # <1>
+    >>> leaf1.ping()    # <2>
+    <instance of Leaf>.ping() in Leaf
+    <instance of Leaf>.ping() in A
+    <instance of Leaf>.ping() in B
+    <instance of Leaf>.ping() in Root
+
+    >>> leaf1.pong()   # <3>
+    <instance of Leaf>.pong() in A
+    <instance of Leaf>.pong() in B
+
+# end::DIAMOND_CALLS[]
+"""
+
+# tag::DIAMOND_CLASSES[]
+class Root:  # <1>
     def ping(self):
-        print('ping:', self)
+        print(f'{self}.ping() in Root')
 
-
-class B(A):
     def pong(self):
-        print('pong:', self)
+        print(f'{self}.pong() in Root')
+
+    def __repr__(self):
+        cls_name = type(self).__name__
+        return f'<instance of {cls_name}>'
 
 
-class C(A):
-    def pong(self):
-        print('PONG:', self)
-
-
-class D(B, C):
-
+class A(Root):  # <2>
     def ping(self):
+        print(f'{self}.ping() in A')
         super().ping()
-        print('post-ping:', self)
 
-    def pingpong(self):
-        self.ping()
-        super().ping()
-        self.pong()
+    def pong(self):
+        print(f'{self}.pong() in A')
         super().pong()
-        C.pong(self)
+
+
+class B(Root):  # <3>
+    def ping(self):
+        print(f'{self}.ping() in B')
+        super().ping()
+
+    def pong(self):
+        print(f'{self}.pong() in B')
+
+
+class Leaf(A, B):  # <4>
+    def ping(self):
+        print(f'{self}.ping() in Leaf')
+        super().ping()
+# end::DIAMOND_CLASSES[]