Single and double asterisks preceding variables in function arguments

[Duncan Booth]

anton muhin <antonmuhin at rambler.ru> wrote in news:bv3gdg$ms0sn$1 at ID-
217427.news.uni-berlin.de:

> 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.

I may be wrong, but I think the OP was asking about calling functions 
rather than defining them. The '*' and '**' before arguments in function 
calls are described in section 5.3.4 of the language reference but, so far 
as I know, isn't explained clearly in any of the more 'user level' text. 
There is a brief mention in the library reference under the documention of 
'apply'.

In a call of the form:

   myfunction(x, *someargs, **someotherargs)

the sequence 'someargs' is used to supply a variable number of additional 
positional arguments. 'someotherargs' should be a dictionary and is used to 
supply additional keyword arguments.