Passing functions which have multiple return values as arguments in Python

So, Python functions can return multiple values. It struck me that it would be convenient (though a bit less readable) if the following were possible.

a = [[1,2],[3,4]]

def cord():
    return 1, 1

def printa(y,x):
    print a[y][x]

printa(cord())

...but it's not. I'm aware that you can do the same thing by dumping both return values into temporary variables, but it doesn't seem as elegant. I could also rewrite the last line as "printa(cord()[0], cord()[1])", but that would execute cord() twice.

Is there an elegant, efficient way to do this? Or should I just see that quote about premature optimization and forget about this?

From stackoverflow

• printa(*cord())
  

  The * here is an argument expansion operator... well I forget what it's technically called, but in this context it takes a list or tuple and expands it out so the function sees each list/tuple element as a separate argument.

  It's basically the reverse of the * you might use to capture all non-keyword arguments in a function definition:

  def fn(*args):
      # args is now a tuple of the non-keyworded arguments
      print args
  
  fn(1, 2, 3, 4, 5)
  

  prints (1, 2, 3, 4, 5)

  fn(*[1, 2, 3, 4, 5])
  

  does the same.

  Jason Baker : It's a tuple. :-)

  regan : And the documentation: http://docs.python.org/tutorial/controlflow.html#tut-unpacking-arguments

  David Zaslavsky : Thanks Jason, I edited that in.

  Miles : # args is now a tuple...

• Try this:

  >>> def cord():
  ...     return (1, 1)
  ...
  >>> def printa(y, x):
  ...     print a[y][x]
  ...
  >>> a=[[1,2],[3,4]]
  >>> printa(*cord())
  4
  

  The star basically says "use the elements of this collection as positional arguments." You can do the same with a dict for keyword arguments using two stars:

  >>> a = {'a' : 2, 'b' : 3}
  >>> def foo(a, b):
  ...    print a, b
  ...
  >>> foo(**a)
  2 3
  

• Actually, Python doesn't really return multiple values, it returns one value which can be multiple values packed into a tuple. Which means that you need to "unpack" the returned value in order to have multiples. A statement like

  x,y = cord()
  

  does that, but directly using the return value as you did in

  printa(cord())
  

  doesn't, that's why you need to use the asterisk. Perhaps a nice term for it might be "implicit tuple unpacking" or "tuple unpacking without assignment".