What YAML engine do you use?

[Michael Spencer]

Paul Rubin wrote:

> YAML looks to me to be completely insane, even compared to Python
> lists.  I think it would be great if the Python library exposed an
> interface for parsing constant list and dict expressions, e.g.:
> 
>    [1, 2, 'Joe Smith', 8237972883334L,   # comment
>       {'Favorite fruits': ['apple', 'banana', 'pear']},  # another comment
>       'xyzzy', [3, 5, [3.14159, 2.71828, []]]]
> 
> I don't see what YAML accomplishes that something like the above wouldn't.
> 
> Note that all the values in the above have to be constant literals.
> Don't suggest using eval.  That would be a huge security hole.
Not hard at all, thanks to compiler.ast:

 >>> import compiler
  ...
  >>> class AbstractVisitor(object):
  ...     def __init__(self):
  ...         self._cache = {} # dispatch table
  ...
  ...     def visit(self, node,**kw):
  ...         cls = node.__class__
  ...         meth = self._cache.setdefault(cls,
  ...             getattr(self,'visit'+cls.__name__,self.default))
  ...         return meth(node, **kw)
  ...
  ...     def default(self, node, **kw):
  ...         for child in node.getChildNodes():
  ...             return self.visit(child, **kw)
  ...
  >>> class ConstEval(AbstractVisitor):
  ...     def visitConst(self, node, **kw):
  ...         return node.value
  ...
  ...     def visitName(self,node, **kw):
  ...         raise NameError, "Names are not resolved"
  ...
  ...     def visitDict(self,node,**kw):
  ...         return dict([(self.visit(k),self.visit(v)) for k,v in node.items])
  ...
  ...     def visitTuple(self,node, **kw):
  ...         return tuple(self.visit(i) for i in node.nodes)
  ...
  ...     def visitList(self,node, **kw):
  ...         return [self.visit(i) for i in node.nodes]
  ...
  >>> ast = compiler.parse(source,"eval")
  >>> walker = ConstEval()
  >>> walker.visit(ast)
[1, 2, 'Joe Smith', 8237972883334L, {'Favorite fruits': ['apple', 'banana', 
'pear']}, 'xyzzy', [3, 5, [3.1415899999999999, 2.71828, []]]]

Add sugar to taste

Regards

Michael