[Tutor] What is the square bracket about?

[Danny Yoo]

>> def adder1(*args):
>>      print 'adder1',
>>      if type(args[0]) == type(0):
>>          sum = 0
>>      else:
>>          sum = args[0][:0]
>>      for arg in args:
>>          sum = sum + arg
>>      return sum


This function looks overly enamored with Python slicing.  *grin* Unless 
I'm missing something, this function can be simplified to:

####################################################################
def adder(*args):
     """Sum up a list of args, assuming that the list is nonempty."""
     running_sum = args[0]
     for element in args[1:]:
         running_sum = running_sum + element
     return running_sum
####################################################################

That is, in stilted English: take the first element, and treat that as our 
initial sum.  Run through the rest of the elements, and add each such 
element to our running sum.  At the end of the iteration, we should be 
done, and our running subtotal sum should be the sum of all the elements.