visitor_design_pattern package

Submodules

visitor_design_pattern.visitor_design_pattern module

Visitor Design Pattern main module

This module defines the main component exposed by the visitor-design-pattern package:

• visitor class decorator

• traverse method decorator

• prefix method decorator

• infix method decorator

• suffix method decorator

• Visitable interface

class visitor_design_pattern.visitor_design_pattern.VisitableInterface

Bases: object

Base class for visited nodes of the data structure

accept(visitor, parent_res=None)

Default accept method

This method implement the base logic of the traversal.

A complex data structure may need a custom implementation. In that case users may subclass the VisitableInterface and implement their own traversal logic.

Parameters:

• visitor: class decorated by the visitor class decorator

• parent_res: return value of the prefix call of visitor on the current node’s parent

visitor_design_pattern.visitor_design_pattern.infix()

infix visit method decorator

Equivalent to traverse(‘infix’)

visitor_design_pattern.visitor_design_pattern.prefix()

prefix visit method decorator

Equivalent to traverse(‘prefix’)

visitor_design_pattern.visitor_design_pattern.suffix()

suffix visit method decorator

Equivalent to traverse(‘suffix’)

visitor_design_pattern.visitor_design_pattern.traverse(traversal_mode)

visit method decorator

Mark a method as visit method

Usage:

@visitor()
def MyVisitor():

    @traverse("prefix")
    def my_visit_method(self, node: Type):
        ...

    ...

Parameters:

• traversal_mode: “prefix”, “infix” or “suffix” or list

  The specified mode defines when the visit method should be called when traversing the structure.

  A list of multiple modes can be specified.

visitor_design_pattern.visitor_design_pattern.visitor(traversal_mode=None)

visitor class decorator

Mark a class cls as visitor. This initializes the supported VISITABLE_TYPES dict in cls, and gather the different visit method marked with the traverse, prefix, infix or suffix decorators

Usage:

@visitor()
def MyVisitor():
    ...

Parameters:

• traversal_mode: None, “prefix”, “infix” or “suffix”

  Specifying a non None traversal_mode prevents other modes to be used in the decorated visitor

Module contents

Top-level package for Visitor Design Pattern.