[Python-Dev] Examples for PEP 572
Steven D'Aprano
steve at pearwood.info
Wed Jul 4 12:02:47 EDT 2018
On Wed, Jul 04, 2018 at 10:20:35AM -0400, David Mertz wrote:
> Hmmm... I admit I didn't expect quite this behavior. I'm don't actually
> understand why it's doing what it does.
>
> >>> def myfun():
> ... print(globals().update({'foo', 43}), foo)
Try it with a dict {'foo': 43} instead of a set :-)
> ...
> >>> myfun()
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> File "<stdin>", line 2, in myfun
> TypeError: cannot convert dictionary update sequence element #0 to a
> sequence
I think Chris meant to try it inside a function using locals() rather
than globals.
> That said, this is a silly game either way. And even though you CAN
> (sometimes) bind in an expression pre-572, that's one of those perverse
> corners that one shouldn't actually use.
Still, it is sometimes useful to explore scoping issues by using
globals() and/or locals() to see what happens. But I would really
hesitate to use them in production unless I was really careful.
--
Steve
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