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

Guido van Rossum guido at python.org
Mon Dec 13 17:54:16 CET 2010

On Mon, Dec 13, 2010 at 5:42 AM, Tres Seaver <tseaver at palladion.com> wrote:
> I actually make use of the feature when dealing with APIs which both a)
> take lots of arguments (more than fit comfortably on two lines at
> whatever indentation they are called), and b) have optional trailing
> arguments:  I always leave the trailing comma in place in such cases,
> with the closing paren on the following line, so that adding or removing
> an argument at the end of the list stays consistent (the diffs are
> better, too, when I use this pattern).

Same here, and it's a soft style rule at Google that trailing commas
are good -- they can help produce shorter diffs. I'm at least +0 on
allowing trailing commas in the situation the OP mentioned.

--Guido van Rossum (python.org/~guido)

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