Single and double asterisks preceding variables in function arguments

[Stephen Boulet]

anton muhin wrote:

> Stephen Boulet wrote:
> 
>> I've run across code like "myfunction(x, *someargs, **someotherargs)", 
>> but haven't seen documentation for this.
>>
>> Can someone fill me in on what the leading * and ** do? Thanks.
>>
>> Stephen
> 
> 
> See item 7.5 in Language Reference. In short: * declaries list of 
> additional parameters, while ** declares map of additional parameters. 
> Try somehting like:
> 
>     def foo(*params): print params
> 
> and
> 
>     def bar(**params): print params
> 
> to find out details.
> 
> regards,
> anton.

<<
a={'c1':'red','c2':'blue','c3':'fusia'}
def bar(**params):
....for k in params.keys():
........print k, params[k]
bar(a)
Traceback (most recent call last):
   File "<input>", line 1, in ?
TypeError: bar() takes exactly 0 arguments (1 given)
 >>

Why does bar take zero arguments?

Hmm, but:

<<
def bar2(*params,**moreparams):
....print "params are ", params,'\n'
....for k in moreparams.keys():
........print k, moreparams[k]
....print "moreparams are ", moreparams

bar2(range(3),a,)
params are  ([0, 1, 2], {'c3': 'fusia', 'c2': 'blue', 'c1': 'red'})

moreparams are  {}
 >>

I think I've got the *params argument down (you just get the whole 
argument list), but I'm still not getting the **moreparams ...

Stephen