[Tim]
>> ...
>> Worm around that too, then going back to the example at the top, if
>> the manager's
>>
>> locals().update(_locals)
>>
>> had the intended effect, it would end up restoring `b` to 2 too, yes?
>> The only names that "should be" restored are the names in the `kws`
>> dict.
[David]
> Actually, that wasn't my intention. As I imagined the semantics, I wanted a
> context manager that restored the "outside" context for anything defined
> "inside" the context. Allowing keyword arguments was just an extra
> "convenience" that was meant to be equivalent to defining/overwriting
> variables inside the body. So these would be equivalent:
>
> ## 1
> with sublocal():
> a = 1
> b = 2
> x = a + b
> # a, b now have their old values again
What about x? I assume that's also restored.
> ## 2
> with sublocal(a=1, b=2):
> x = a + b
> # a, b now have their old values again
>
> ## 3
> with sublocal(a=1):
> b = 2
> x = a + b
> # a, b now have their old values again
>
> I knew I was ignoring nonlocals and nested function scopes. But just trying
> something really simple that looks like the un-proposal in some cases.
> Maybe there's no way in pure-Python to deal with the edge cases though.
Or even just locals - there doesn't appear to be any supported way in
Python 3 for even `exec` to reliably change locals anymore.
If the intent is to create an "honest-to-Guido new Python scope", then
I expect changing
BLOCK_OF_CODE
to
def unique_name():
BLOCK_OF_CODE
unique_name()
del unique_name
gets pretty close? Any name "created" inside BLOCK_OF_CODE would be
tagged by the compiler as function-local, and vanish when the function
returned. Anything merely referenced would inherit the enclosing
function's meaning.
I can think of some warts. E.g., after
global g
if BLOCK_OF_CODE were
g += 1
then wrapping that line alone in a function would lead to an
UnboundLocalError when the function was called (because the `global g`
isn't "inherited").
Anyway, since I've never done that in my life, never saw anyone else
do it, and never even thought of it before today, I'm pretty confident
there isn't a hitherto undetected groundswell of demand for a quick
way to create an honest-to-Guido new Python scope ;-)
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