[Python-Dev] A grammatical oddity: trailing commas in argument lists.

Eric Smith eric at trueblade.com
Fri Jul 9 18:36:01 CEST 2010

On 7/9/10 10:40 AM, Mark Dickinson wrote:
> While looking at a parser module issue
> (http://bugs.python.org/issue9154) I noticed that Python's grammar
> doesn't permit trailing commas after keyword-only args.  That is,
>      def f(a, b,):  pass
> is valid syntax, while
>      def f(*, a, b,): pass
> is not.  I was just curious whether the latter was deliberate or an
> oversight.  And if an oversight, is it worth fixing after the
> moratorium expires?  (See also http://bugs.python.org/issue2009.)

I use trailing commas all the time in argument lists. I don't use 
keyword-only args much, but I will when I switch to 3.x. I'd like to see 
this fixed. I'd argue it's a bug fix, but that's me.


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