[Python-Dev] AST optimizer implemented in Python

[Nick Coghlan]

Implementations are currently required to *have* an AST (or else declare
non compliance with that particular flag to compile). They're definitely
not required to have the *same* AST, thus all AST manipulation, like
bytecode manipulation, is necessarily implementation dependent.

We don't even guarantee AST compatibility between versions of CPython.

I believe the appropriate warnings are already present in the ast module
docs, but there may be misleading wording elsewhere that needs to be
cleaned up.

Regards,
Nick.

--
Sent from my phone, thus the relative brevity :)
On Aug 14, 2012 5:03 AM, "Terry Reedy" <tjreedy at udel.edu> wrote:

> On 8/13/2012 10:45 AM, Guido van Rossum wrote:
>
>> Not so fast. If you make this a language feature you force all Python
>> implementations to support an identical AST API. That's a big step.
>>
>
> I have been wondering about this. One could think from the manuals that we
> are there already. From the beginning of the ast chapter:
>
> "The ast module helps Python applications to process trees of *the* Python
> abstract syntax grammar.  ... An abstract syntax tree can be generated by
> passing ast.PyCF_ONLY_AST as a flag to the compile() built-in function"
> (emphasis on *the* added).
>
> and the entry for compile(): "Compile the source into a code or AST
> object."
>
> I see nothing about ast possibly being CPython only. Should there be?
>
> --
> Terry Jan Reedy
>
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