hoffmann · August 9, 2010 14:46 · Aug 9, 2010 · Aug 9, 2010 · Aug 9, 2010
diff --git a/extrinsic_visitor_inheritance.py b/extrinsic_visitor_inheritance.py
@@ -2,7 +2,7 @@
 Implementation of the Extrinsic Visitor Pattern in Python with support
 for Inheritance.
 
-see: http://peak.telecommunity.com/DevCenter/VisitorRevisited
+see: http://peter-hoffmann.com/2010/extrinsic-visitor-pattern-python-inheritance.html
 """
 
 class Node(object): pass

diff --git a/extrinsic_visitor_inheritance.py b/extrinsic_visitor_inheritance.py
@@ -37,3 +37,10 @@ def visit_B(self, node, *args, **kwargs):
 visitor.visit(a)
 visitor.visit(b)
 visitor.visit(c)
+
+
+"""
+generic_visit A
+visit_B B
+visit_B C
+"""
diff --git a/extrinsic_visitor_inheritance.py b/extrinsic_visitor_inheritance.py
@@ -0,0 +1,39 @@
+"""
+Implementation of the Extrinsic Visitor Pattern in Python with support
+for Inheritance.
+
+see: http://peak.telecommunity.com/DevCenter/VisitorRevisited
+"""
+
+class Node(object): pass
+class A(Node): pass
+class B(Node): pass
+class C(A,B): pass
+
+class Visitor(object):
+    def visit(self, node, *args, **kwargs):
+        meth = None
+        for cls in node.__class__.__mro__:
+            meth_name = 'visit_'+cls.__name__
+            meth = getattr(self, meth_name, None)
+            if meth:
+                break
+
+        if not meth:
+            meth = self.generic_visit
+        return meth(node, *args, **kwargs)
+
+    def generic_visit(self, node, *args, **kwargs):
+        print 'generic_visit '+node.__class__.__name__
+
+    def visit_B(self, node, *args, **kwargs):
+        print 'visit_B '+node.__class__.__name__
+
+
+a = A()
+b = B()
+c = C()
+visitor = Visitor()
+visitor.visit(a)
+visitor.visit(b)
+visitor.visit(c)