Set a flag on the function or a global?

[Chris Angelico]

On Tue, Jun 16, 2015 at 10:20 AM, Ben Finney <ben+python at benfinney.id.au> wrote:
> Chris Angelico <rosuav at gmail.com> writes:
>
>> On Tue, Jun 16, 2015 at 9:57 AM, Steven D'Aprano
>> <steve+comp.lang.python at pearwood.info> wrote:
>> > I can use a flag set on the function object itself:
>> >
>> > edir.dunders = False
>>
>> For most situations, the last one is extremely surprising - attributes
>> on functions aren't normally meant to be changed by outside callers,
>> it always feels wrong (they belong to the function itself).
>
> I'm surprised by your assertion. To my mind, outside callers get simple
> and direct access to the attribute, whereas the code of the function
> itself does not have such easy access; unlike ‘self’ for the current
> instance of a class, there's no obvious name to use for referring to the
> function object within the function object's own code.
>
> In what sense do they “belong to” the function itself *more than* to
> outside callers?

Custom function attributes (as in, those not set by the interpreter
itself) are pretty rare, but I've usually seen them only being defined
by the module that created them. Setting that kind of attribute
externally, from a different module, seems odd - and undiscoverable.
But for interactive work, that should be fine.

ChrisA