1 #!/usr/bin/env python 2 3 class Branch: 4 def __init__(self, nodes): 5 self.nodes = nodes 6 7 class Leaf: 8 def __init__(self, value): 9 self.value = value 10 11 class Visitor: 12 def visit(self, node): 13 method = getattr(self, node.__class__.__name__) 14 return method(node) 15 16 # Visitor-specific functionality. 17 # Note that getattr does not support "visit" + __class__.__name__. 18 19 def Branch(self, node): 20 sum = 0 21 for node in node.nodes: 22 sum += self.visit(node) 23 return sum 24 25 def Leaf(self, node): 26 return node.value 27 28 tree = \ 29 Branch(( 30 Branch(( 31 Leaf(10), 32 Leaf(5) 33 )), 34 Leaf(2) 35 )) 36 37 visitor = Visitor() 38 result_17 = visitor.visit(tree) 39 40 # vim: tabstop=4 expandtab shiftwidth=4
