Implemented Visitor pattern

pypatterns/behavioral/visitor.py

@@ -0,0 +1,50 @@
+from abc import ABCMeta, abstractmethod
+
+
+class Visitor(metaclass=ABCMeta):
+    """
+    Abstract Visitor class as part of the Visitor Design Pattern.
+    """
+    def visit(self, node, *args, **kwargs):
+        """
+        Visit the visitor with some object.
+
+        @param node: An object to call a visitor method with.
+        @param args: Arguments to go with the visitor method call.
+        @param kwargs: Keyword arguments to go with the visitor method call.
+        @return: The return value of the method that was called for visiting object.
+        """
+        method = None
+        for cls in node.__class__.__mro__:
+            method_name = 'visit_'+cls.__name__.lower()
+            method = getattr(self, method_name, None)
+            if method:
+                break
+
+        if not method:
+            method = self.generic_visit
+        return method(node, *args, **kwargs)
+
+    @abstractmethod
+    def generic_visit(self, node, *args, **kwargs):
+        """
+        The method to call if no methods were found for a visiting object.
+
+        @param node: An object to call a visitor method with.
+        @param args: Arguments to go with the visitor method call.
+        @param kwargs: Keyword arguments to go with the visitor method call.
+        """
+
+
+class Visitee(object):
+    """
+    A base class for objects that wish to be able to visit a Visitor class.
+    """
+    def accept(self, visitor):
+        """
+        Visit a visitor with this class instance.
+
+        @param visitor: The visitor to visit.
+        @type visitor: Visitor
+        """
+        return visitor.visit(self)