Questions about `locals` builtin

[dieter]

Kirill Balunov <kirillbalunov at gmail.com> writes:
>  2018-02-27 2:57 GMT+03:00 Terry Reedy <tjreedy at udel.edu>:
>
>> The point of point 3 is that terminology and details would likely be
>> different if Python were freshly designed more or less as it is today, and
>> some things only make more or less sense in historical context. Learn what
>> you need to know to write code that works.
>>
>
> Thank you, I'm fairly familiar with the scope and namespace concepts in
> Python 3, and they are also very well described in the "Execution model"
> https://docs.python.org/3/reference/executionmodel.html#execution-model,
> for this special thanks to the person who wrote it ;-)
>
> I started using Python with СPython 3.5 and I'm not familiar with the
> Python 2 features. But since Python 2 got into our discussion, I still have
> a question:
>
> a.  Is this restriction for locals desirable in the implementation of
> CPython in Python 3?
> b.  Or is it the result of temporary fixes for Python 2?

I think it is an implementation artefact: for efficiency reasons,
local variables in a function are handled differently than "local"
variables elsewhere. A side effect of the concrete implementation
causes that truely local variables cannot be changed by updating
the result of "locals()". The "locals" documentation tries to
document the restrictions.