parse-time optimizations

[Michael Hudson]

Thomas Wouters <thomas at xs4all.net> writes:

> No need to look at the source. You can write the optimizations in
> Python.  All you need is the marshal module, the dis module and some
> creative disk work (to make the code attributes effectively writable
> -- M.'s bytecodehacks might help here, I haven't checked

bytecodehacks has a "rationalize" module, mostly written by Corran
Webster, that does constant folding, and some jump-jump optimizations
(nad maybe some other stuff, I haven't looked at it in ages).

Thing is, if you're writing code that benefits from constant folding -
WHY?  If your code contains things like:

    "a" + "b"

then you have bigger problems than Python's lack of optimizations...

> ): keep track of which vrbls are constants (start by looking for
> 'LOAD_CONST' opcodes) and replace them where necessary. Don't forget
> to keep a jump-offset table when you collapse instructions, and
> adjust all jumps correctly, or you'll end up jumping into outer
> space.

This is why you want to use bytecodehacks - they do all this for you.

Of course they don't work properly for Python 2.1...

Cheers,
M.

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