Package TestON :: Package core :: Module ast :: Class NodeTransformer
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Class NodeTransformer

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A :class:`NodeVisitor` subclass that walks the abstract syntax tree and allows modification of nodes.

The `NodeTransformer` will walk the AST and use the return value of the visitor methods to replace or remove the old node. If the return value of the visitor method is ``None``, the node will be removed from its location, otherwise it is replaced with the return value. The return value may be the original node in which case no replacement takes place.

Here is an example transformer that rewrites all occurrences of name lookups (``foo``) to ``data['foo']``:

  class RewriteName(NodeTransformer):

      def visit_Name(self, node):
          return copy_location(Subscript(
              value=Name(id='data', ctx=Load()),
              slice=Index(value=Str(s=node.id)),
              ctx=node.ctx
          ), node)

Keep in mind that if the node you're operating on has child nodes you must either transform the child nodes yourself or call the :meth:`generic_visit` method for the node first.

For nodes that were part of a collection of statements (that applies to all statement nodes), the visitor may also return a list of nodes rather than just a single node.

Usually you use the transformer like this:

  node = YourTransformer().visit(node)
Instance Methods [hide private]
 
generic_visit(self, node)
Called if no explicit visitor function exists for a node.
source code
 
visit(self, node)
Visit a node. (Inherited from TestON.core.ast.NodeVisitor)
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Inherited from object: __delattr__, __format__, __getattribute__, __hash__, __init__, __new__, __reduce__, __reduce_ex__, __repr__, __setattr__, __sizeof__, __str__, __subclasshook__

Properties [hide private]

Inherited from object: __class__

Method Details [hide private]

generic_visit(self, node)

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Called if no explicit visitor function exists for a node.

Overrides: NodeVisitor.generic_visit
(inherited documentation)