Parsing a list of numbers in Python

I find that I often need to get a selection of numbers in a range as input. I'm using Python more and more these days it seems, so I needed to port this classic function over. I must have done this 4 weeks ago - I'd been meaning to put it up here.

The valid input will be a comma separated list of integers, which could possibly contain a 'range' defined as "x-y" - where x and y are both integers.

I tried not to make any special stipulation for the order of these integers, or even that the input string would not contain bad characters.

Here it is:

#! /usr/local/bin/python
import sys
import os

# return a set of selected values when a string in the form:
# 1-4,6
# would return:
# 1,2,3,4,6
# as expected...

def parseIntSet(nputstr=""):
  selection = set()
  invalid = set()
  # tokens are comma seperated values
  tokens = [x.strip() for x in nputstr.split(',')]
  for i in tokens:
     try:
        # typically tokens are plain old integers
        selection.add(int(i))
     except:
        # if not, then it might be a range
        try:
           token = [int(k.strip()) for k in i.split('-')]
           if len(token) > 1:
              token.sort()
              # we have items seperated by a dash
              # try to build a valid range
              first = token[0]
              last = token[len(token)-1]
              for x in range(first, last+1):
                 selection.add(x)
        except:
           # not an int and not a range...
           invalid.add(i)
  # Report invalid tokens before returning valid selection
  print "Invalid set: " + str(invalid)
  return selection
# end parseIntSet

print 'Generate a list of selected items!'
nputstr = raw_input('Enter a list of items: ')

selection = parseIntSet(nputstr)
print 'Your selection is: '
print str(selection)

When trying to copy this from someone else I came across a similar function written in Ruby, in case you needed that instead.