PYTHON detecting consecutive integers in a list

page_range.py

# Ref from http://stackoverflow.com/questions/2361945/detecting-consecutive-integers-in-a-list

from itertools import groupby
from operator import itemgetter

class PageRange(object):

    @staticmethod
    def to_text_range(array_of_numbers):
        text_buffer = []

        for k, g in groupby(enumerate(sorted(array_of_numbers)), lambda (i,x):i-x):
            val = PageRange._create_text(map(itemgetter(1), g)) 
            text_buffer.append(val)

        return ','.join(text_buffer)

    @staticmethod
    def _create_text(run):
        if len(run) == 1:
            return run[0].__str__()
        return "{0}-{1}".format(run[0], run[-1])

tests_page_range.py

import unittest
from nose.tools import *

class PageRangeSinglePageTestCase(unittest.TestCase):
   def test_full_range(self):
        test = PageRange.to_text_range(range(1,51))
        assert_equal("1-50", test)
            
    def test_ranges_and_single_pages(self):
        pr = [1,5,9,10,11] + range(20, 31) + [99,105,120] + range(150, 161) + [800]
        test = PageRange.to_text_range(pr)
        assert_equal("1,5,9-11,20-30,99,105,120,150-160,800", test)