Rats! vararg assignments don't work

[Gary Herron]

samwyse wrote:
> I'm a relative newbie to Python, so please bear with me.  After seeing 
> how varargs work in parameter lists, like this:
>      def func(x, *arglist):
> and this:
>      x = func(1, *moreargs)
> I thought that I'd try this:
>      first, *rest = arglist
> Needless to say, it didn't work.  That leaves me with two questions.
>
> First, is there a good way to do this?  For now, I'm using this:
>      first, rest = arglist[0], arglist[1:]
> but it leaves a bad taste in my mouth.
>   
Well, your moreargs parameter is a tuple, and there are innumerable ways
to process a tuple. (And even more if you convert it to a list.)

If you are just interested in extracting only the first arg, then your
code is quite Pythonic.  However, if you are going to do that in a loop
to successively process  each arg, the you have several better options:

For instance:
  for arg in moreargs:   # Loop through each arg
      <do something with arg>

or

  for i in range(len(moreargs)):
      <do something with morergs[i]>  # Extract ith arg

or

argslist = list(moreargs)
while argslist:
  firstarg = argslist.pop(0) # Extract first arg
  <do something with firstarg>

Gary Herron

> Second, is there any good reason why it shouldn't work?  It seems like 
> such an obvious idiom that I can't believe that I'm the first to come up 
> with the idea.  I don't really have the time right now to go source 
> diving, so I can't tell if it would be wildly inefficient to implement.
>
> Thanks!
>