An implementation of the visitor pattern for Python.
Find more details at Follow-Up to Python Visitor.
Works on both Python 2 and 3. Specifically tested on 2.7.2, 2.7.5, 3.3.2, 3.3.5, and 3.4.0.
First, import the module.
import visitorThen, define a class that you want to act as the visitor.
class SomeVisitor(object):
passThen, mark the method and parameter that provides dynamic dispatching.
class SomeVisitor(object):
@visitor.on('node') # Note the name of the parameter in the on decorator
def visit(self, node);
passNow, override the method on classes that you want called specifically based on the type of the argument.
class SomeVisitor(object):
@visitor.on('node') # Note the name of the parameter in the on decorator
def visit(self, node);
pass
@visitor.when(MyFirstClass)
def visit(self, node):
print 'I am going first class!'
@visitor.when(MyOtherClass)
def visit(self, node):
print 'Whatever. Boring.'> git clone [email protected]:realistschuckle/pyvisitor.git
> cd pyvisitor
> python example
Creating the abstract syntax tree that contains x = 5
and printing it
x=5
Creating me and my dependents and printing them
- Curtis
- Son
- Daughter
- Lola a Shitzu