On Wed, Feb 17, 2016 at 3:32 PM, Pavel Stehule <pavel.stehule@gmail.com> wrote: >> Python 3 has keyword only arguments. It occurs to me they're exactly >> for "optional extra stuff" like detail, hint etc. >> Python 2 doesn't have that notion but you can kind of fake it since >> you get an args tuple and a kwargs dictionary. > > > I prefer a possibility to use both ways - positional form is shorter, > keywords can help with some parameters. > > But I cannot to imagine your idea, can you show it in detail?
Sure, what I mean is:
plpy.error('msg') # as before produces message 'msg' plpy.error(42) # as before produces message '42', including the conversion of the int to str plpy.error('msg', 'arg 2 is still part of msg') # as before, produces message '('msg', 'arg2 is still part of msg')' # and so on for as many positional arguments, nothing changes # I still think allowing more than one positional argument is unfortunate but for compatibility we keep allowing more
# to pass detail you MUST use keyword args to disambiguate "I really want detail" vs. "I have argument 2 which is part of the messsage tuple for compatibility" plpy.error('msg', 42, detail='a detail') # produces message '('msg', 42)' and detail 'a detail' plpy.error('msg', detail=77) # produces message 'msg' and detail '77' so detail is also converted to str just like message for consistency # and so on for the others plpy.error('msg', 42, detail='a detail', hint='a hint') plpy.error('msg', 42, schema='sch')
Only keyword arguments are treated specially and we know no existing code has keyword arguments since they didn't work before.
Implementation wise, it's something like this but in C: