[Tutor] dynamic argument lists

[eShopping]

Bob, Kent

thanks for the suggestions.  Bob made the comment "If there is no 
compelling requirement that myfunc's argument be in the form **kwargs 
...", but I'm afraid I don't understand the difference between

myfunc (**kwargs)

and

myfunc (kwargs)

Would someone mind explaining this?  I never managed to find a 
satisfactory explanation for what "**" means!

Alun Griffiths

 > <etrade.griffiths at dsl.pipex.com> wrote:
> > > Hi
> > >
> > > I have a GUI program that extracts some information from the user as
> > > strings, and I then want to use the strings to form an argument list to
> > > another function.  Hopefully the following code gives some flavour:
> > >
> > > def myfunc(**kwargs):
> > >    while kwargs:
> > >        name, value = kwargs.popitem()
> > >        print name, value
> > >
> > > myfunc(a=1, b=2, c=3, d=4)
> > > arg_str = "a=1, b=2, c=3, d=4"
> > > myfunc(arg_str)
> > >
> > > ARG_STR will be built up from the data extracted from the GUI.  I get
> > this
> > > error
> > >
> > > TypeError: myfunc() takes exactly 0 arguments (1 given)
> > >
> > > I understand that ARG_STR is a string and that MYFUNC is expecting
> > something
> > > else ,,, but not sure what it is.  I have tried various dictionary
> > > configurations such as
> > >
> > > arg1 = ["a","b","c","d"]
> > > arg2 = [1,2,3,4]
> > > arg3 = dict(zip(arg1,arg2))
> > > myfunc(arg3)
> >
>
>  myfunc(**arg3)
>
>Let's back up to arg_str = "a=1, b=2, c=3, d=4"
>
>To create a dictionary from that:
>
>argDict = dict(pair.split('=') for pair in arg_str.split(','))
>
>If there is no compelling requirement that myfunc's argument be in the form
>**kwargs then
>
>def myfunc(kwargs):
>     while kwargs:
>         name, value = kwargs.popitem()
>         print name, value
>
>myfunc(argDict)