[Python-ideas] fixing mutable default argument values

Joel Bender jjb5 at cornell.edu
Wed Jan 17 15:19:19 CET 2007

> Where the <>s indicate these special semantics.

The syntax bothers me, but launched an idea: How about separating 
parameter default value issues from instance specific definition time 

     def foo(a, b=4, c=None):
         local d = Bar([2,3,4])

The function code can decide if it wants to use c, provided by the 
caller, or d when no value for c is given.  The developer may decide 
that None is not a good value for 'no value for c', but that's a design 

You can do this now with:

     def foo(a, b=4, c=None):

     foo.func_dict['d'] = Bar([2,3,4])

But I would rather see this inside foo(), jamming variables into the 
func_dict bothers me too :-).

The new keyword would work for classes, but be a functional noop:

     class Snorf:
         local eggs = 3
         spam = 4


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