[Python-Dev] PEP 3102: Keyword-only arguments

[Edward Loper]

Terry Reedy wrote:
> There are two subproposals: first, keyword-only args after a variable 
> number of positional args, which requires allowing keyword parameter 
> specifications after the *args parameter, and second, keyword-only args 
> after a fixed number number of positional args, implemented with a naked 
> '*'.  To the first, I said "The rationale for this is pretty obvious.".  To 
> the second, I asked, and still ask, "Why?".

I see two possible reasons:

   - A function's author believes that calls to the function will be
     easier to read if certain parameters are passed by name, rather
     than positionally; and they want to enforce that calling
     convention on their users.  This seems to me to go against the
     "consenting adults" principle.

   - A function's author believes they might change the signature in the
     future to accept new positional arguments, and they will want to put
     them before the args that they declare keyword-only.

Both of these motivations seem fairly weak.  Certainly, neither seems to 
warrant a significant change to function definition syntax.

But perhaps there are other use cases that I'm failing to consider. 
Anyone know of any?

-Edward