Function params with **? what do these mean?

[Dave Hansen]

On 20 Mar 2006 12:46:43 -0800 in comp.lang.python, "J Rice"
<rice.jeffrey at gmail.com> wrote:

>I'm sorry for such a basic question, but I haven't been able to phrase
>a search that gets me an answer and my books are totally silent on
>this.  I have seen a number of python function defs that take
>parameters of the form (**param1).  Looks like a pointer... but my
>books on python (basic as they are) don't make a mention.  What is
>this?

It's a way of accepting a varying number of named arguments.  In the
function, the parameter becomes a dictionary with parameter names as
the keys corresponding to the passed parameter values.

It's harder to explain than understand.  Try playing with the
following function in the python interpreter:

   def test(a,b='b', *c, **d):
      print a,b,c,d

A couple suggestions for tests:

   test(1,2,3,4)
   test(a=1,b=2,c=3,d=4)
   test(2,4,6,8,10,12,ralph=23,tony=45)

See what happens.  Should be mostly self-explanatory.

Regards,
                                        -=Dave

-- 
Change is inevitable, progress is not.