[Tutor] design advice for function

[Christopher Spears]

I got my function to work!  It takes arguments and
adds them:

def adder(**args):
    argsList = args.values()
    sum = argsList[0]
    for x in argsList[1:]:
        sum = sum + x
    return sum

print adder()
print "---"
print adder(a=5)
print "---"
print adder(a=5,b=6)
print "---"
print adder(a=5,b=6,c=7)
print "---"
print adder(ugly=7, good=6, bad=5)
print "---"

However, if I run the above code.  I get an error:

Traceback (most recent call last):
  File "C:\Documents and Settings\Christopher
Spears\My
Documents\programming\PythonScripts\Part4\Ex04\adder.py",
line 8, in -toplevel-
    print adder()
  File "C:\Documents and Settings\Christopher
Spears\My
Documents\programming\PythonScripts\Part4\Ex04\adder.py",
line 3, in adder
    sum = argsList[0]
IndexError: list index out of range

This is caused by the line: print adder().  Obviously
if adder() doesn't receive any arguments, it can't
build the lists resulting in an IndexError.  What is
the best way to solve this?  Should I write some
syntax into the function to check for arguments? 
Should I just write a seperate function to check for arguments?