title: converting a list of integers into range in python
body: <p>Is there something existing in python that can convert an increasing list of integers into a range list</p>
  
  <p>E.g. given the set {0, 1, 2, 3, 4, 7, 8, 9, 11} I want to get { {0,4}, {7,9}, {11,11} }. </p>
  
  <p>I can write a program to do this, but want to know if there is an inbuilt function in python</p>