[Python-ideas] Tweaking closures and lexical scoping to include the function being defined

Paul Moore p.f.moore at gmail.com
Thu Sep 29 16:05:58 CEST 2011

On 29 September 2011 14:30, Nick Coghlan <ncoghlan at gmail.com> wrote:
>    @nonlocal(n=0, lock=threading.Lock())
>    def global_counter():
>        with lock:
>            n += 1
>            return n
> It's presence in the decorator list hints that this is something
> happening outside the functions ordinary local scope, as well as
> indicating when the initialisation happens. The 'nonlocal' then ties
> in with how they behave from the point of view of the code in the
> function body.

I agree, this is a nice option. My biggest discomfort with it is the
idea of a magic decorator name handled specially by the compiler (and
worse still, it's a keyword so it's syntactically very weird indeed).
I had similar discomfort over the new super, but I could get over that
by simply assuming that super was a normal function that was just more
magical than I understood. "@keyword" decorators don't even fit into
my model of valid syntax :-(

That said, I like it otherwise. The above says to me "the following
values are nonlocal to this function", which I can read exactly the
way it actually works. Whether that's a result of a week's immersion
in Nick's propaganda, I can't say, though :-)


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