Grako is a PEG parser builder in Python: https://bitbucket.org/apalala/grako In grako, there's code to synthesize AST node types according to annotations in the grammar whenever a type is not previously provided. This is the code: def _get_nodetype(self, typename): typename = str(typename) if typename in self.nodetypes: return self.nodetypes[typename] # synthethize a new type nodetype = type(typename, (self.baseType,), {}) self._register_nodetype(nodetype) return nodetype It works, but the classes thus created are "weird". I don't remember the details right now, but I think they don't have a proper module or qualname. This particular feature (exploiting this Python capability) is very useful in the early stages of developing a parser, while most of the work goes into debugging the grammar. Having a nice AST produced cheaply is of great value. Cheers, -- Juancarlo *Añez*