List of non-default commodities?

[Dave Peticolas]

Derek Atkins writes:
> Is there a convenient way to get the list of all non-default
> commodities?  What I want to do is grab the list of all commodities
> defined within book, but I don't need the commodities that are
> pre-defined in Gnucash.
> 
> Unfortunately the commodity_table contains all of them, so walking
> through that gives me everything.  That's not what I want.
> 
> Any ideas?

Any commodity in the ISO4217 namespace is a default commodity.
All other commodities are not defaults.

dave