Allow initialiser arguments to be mapped to alternative (private) attribute names

[wallrj]

In Twisted we try hard to limit the public API in new classes so it would be nice if with_init had some way to map an argument name to an alternative private attribute name.

In fact it might even be enough to have a rule that argument names beginning with _ would be stored as private attributes but supplied without the _ prefix.

twisted.python.util.FancyStrMixin has a horrible system where you can supply a tuple of (attr_name, display_name). I suppose you could do something like that here.

Or add a new Attribute class with an argument_name option...and then allow that to be supplied to the characteristic decorators...if you see what I mean.

[hynek]

Yep, I thought about that before.

I guess I would go two ways:

1. Each decorator accepts an Attribute class as you suggest.
2. @attributes additionally adds a convenience argument like private=False that automagically transforms all into _attr if true since that's a rather common case.

Makes sense?

[wallrj]

2 @attributes additionally adds a convenience argument like private=False that automagically transforms all into _attr if true since that's a rather common case.

I think this second option would be convenient, but what I meant in my original comment was that characteristic could implement a policy of always removing leading _ when looking for keyword argument names.

@exarkun is always reminding us that there's no such thing as a private function argument, so maybe he'd approve of that policy.

[hynek]

I think I’ll move this into 14.0 while waiting for glyph sacrificing goats in #9.