[Python-Dev] AST optimizer implemented in Python

Guido van Rossum guido at python.org
Mon Aug 13 16:45:23 CEST 2012

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.

Not that AST manipulation isn't cool -- but I'd like to warn against
over-enthusiasm that might backfire on the language (or its community)
as a whole.


On Mon, Aug 13, 2012 at 1:34 AM, Mark Shannon <mark at hotpy.org> wrote:
> Brett Cannon wrote:
>> On Sat, Aug 11, 2012 at 8:16 PM, Eric Snow <ericsnowcurrently at gmail.com
>> <mailto:ericsnowcurrently at gmail.com>> wrote:
>>     On Sat, Aug 11, 2012 at 6:03 PM, Brett Cannon <brett at python.org
>>     <mailto:brett at python.org>> wrote:
>>      > It would also be very easy to expand importlib.abc.SourceLoader
>>     to add a
>>      > method which is called with source and returns the bytecode to be
>>     written
>>      > out
>>     Yes, please.  Not having to hack around this would be nice.
>> http://bugs.python.org/issue15627
> AST transformation is a lot more general than just optimization.
> Adding an AST transformation is a relatively painless way to add to
> Python the last element of lisp-ness that it lacks:
> Namely being able to treat code as data and transform it at runtime,
> after parsing but before execution.
> Some examples:
> Profiling code be added by an AST transformation.
> IMO this would have been a more elegant way to implement CProfile
> and similar profilers than the current approach.
> AST transformations allow DSLs to be implemented in Python
> (I don't know if that is a + or - ).
> Access to the AST of a function at runtime would also be of use to
> method-based dynamic optimizers, or dynamic de-optimizers for static
> compilers.
> All for the price of adding a single method to SourceLoader.
> What a bargain :)
> Cheers,
> Mark.
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--Guido van Rossum (python.org/~guido)

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