[Python-Dev] Exposing the abstract syntax (original) (raw)
martin at v.loewis.de martin at v.loewis.de
Sun Feb 26 20:59:09 CET 2006
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At PyCon, there was general reluctance for incorporating the ast-objects branch, primarily because people where concerned what the reference counting would do to maintainability, and what (potentially troublesome) options direct exposure of AST objects would do.
OTOH, the approach of creating a shadow tree did not find opposition, so I implemented that.
Currently, you can use compile() to create an AST out of source code, by passing PyCF_ONLY_AST (0x400) to compile. The mapping of AST to Python objects is as follows:
- there is a Python type for every sum, product, and constructor.
- The constructor types inherit from their sum types (e.g. ClassDef inherits from stmt)
- Each constructor and product type has an _fields member, giving the names of the fields of the product.
- Each node in the AST has members with the names given in _fields
- If the field is optional, it might be None
- if the field is zero-or-more, it is represented as a list.
It might be reasonable to expose this through a separate module, in particular to provide access to the type objects.
Regards, Martin
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