[Python-ideas] Give nonlocal the same creating power as global

[Chris Angelico]

On Tue, Sep 12, 2017 at 8:54 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:
> On 12 September 2017 at 03:32, João Matos <jcrmatos at gmail.com> wrote:
>> Hello,
>>
>> You're correct. The idea is to give nonlocal the same ability, redirect
>> subsequent bindings if the variable doesn't exist.
>
> The issue you're facing is that optimised local variables still need
> to be defined in the compilation unit where they're locals - we're not
> going to make the compiler keep track of all the nonlocal declarations
> in nested functions and infer additional local variables from those.
> (It's not technically impossible to do that, it just takes our already
> complex name scoping rules, and makes them even more complex and hard
> to understand).
>
> So in order to do what you want, you're going to need to explicitly
> declare a local variable in the scope you want to write to, either by
> assigning None to it (in any version), or by using a variable
> annotation (in 3.6+). Future readers of your code will thank you for
> making the widget definitions easier to find, rather than having them
> scattered through an arbitrarily large number of nested functions :)

Or, yaknow, the OP could actually use a class, instead of treating a
closure as a poor-man's class...

Honestly, I don't see much advantage to the closure here. A class is a
far better tool for this job IMO.

ChrisA