[Python-ideas] Default arguments in Python - the return - running out of ideas but...

[Pascal Chambon]

Terry Reedy a écrit :
>
> Curt Hagenlocher wrote:
>
>
>> 1. Preventing the "noob" mistake of saying "def f(x = {})" and
>> expecting that a new empty dictionary will be produced for each call,
>> and
>
> As a couple of us have suggested, this, like similar jobs, should be 
> handled by program checkers.  I leave it to someone else to see if 
> existing programs already check and warn and, if not, suggest this to 
> their authors.
>

Indeed, Pylint does handle this in some way :

"W0102: *Dangerous default value %s as argument*
  Used when a mutable value as list or dictionary is detected in a
default value
  for an argument."




Some have talked about thunks or other concepts here ; I too feel that
this issue could be the occasion of introducing new features, that
exceed the scope of default arguments.
Could you peopel develop a little what you think about with "thunk" or 
"early action" ? Is the former different from an argument-less lambda 
function ?


Else, concerning the syntax for "dynamic" default arguments, I guesse 
somethng like :

def func(a, b @= []):
	pass

would be OK, wouldn't it ?

Regards,
Pascal