[Python-Dev] PEP 267 -- is the semantics change OK?

[Jeremy Hylton]

On 10/21/05, Jim Jewett <jimjjewett at gmail.com> wrote:
> (In http://mail.python.org/pipermail/python-dev/2005-October/057501.html)
> Neil Schemenauer suggested PEP 267 as an example of something that
> might be easier with the AST compiler.
>
> As written, PEP 267 does propose a slight semantics change -- but it
> might be an improvement, if it is acceptable.

No, it does not.  PEP 267 suggests a way to preserve the existing
semantics.  You could probably come up with a much simpler approach if
you agreed to change semantics.

Jeremy

> Today, after
>
>     from othermod import val1
>     import othermod
>     val2 = othermod.val2
>     othermod.val3  # Just making sure it was referenced early
>
>     othermod.val1 = "new1"
>     othermod.val2 = "new2"
>     othermod.val3 = "new3"
>
>     print val1, val2, othermod.val3
>
> The print statement will see the updated val3, but will still have
> the original values for val1 and val2.
>
> Under PEP267, all three variables would be compiled to a slot
> access in othermod, and would see the updated objects.
>
> In many cases, this would be a *good* thing.  It might allow
> reload to be rewritten to do what people expect.  On the other
> hand, it would be a change.  Would it be an acceptable change?
>
> -jJ
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