Documenting a function signature (was: Set a flag on the function or a global?)

[random832 at fastmail.us]

On Wed, Jun 17, 2015, at 20:14, Chris Angelico wrote:
> Mostly. That would imply that object is a mandatory parameter, which
> AIUI isn't the case for Steven's edir. The downside of this kind of
> signature is that it's hard to show the parameters that have unusual
> defaults (either sentinel objects and custom code to cope, or they're
> pulled out of *a or **kw).

My instinct would be to put =... for that case and explain in the
documentation "If foo is not provided, [behavior]".

Of course, that runs the risk of people thinking you actually mean
Ellipsis, or that providing Ellipsis explicitly will give the same
behavior as the default.