title: Python/sage: can lists start at index 1?
body: <p>I've downloaded from a supposedly serious source a sage script. It doesn't work on my computer, and a quick debugging showed that a problem came from the fact that at some point, the authors were doing as if a n-element list was numbered from 1 to n (whereas the “normal” numbering in Python and (thus) sage is 0..n-1).</p>
  
  <p>What am I missing? Is there a global variable hidden somewhere that changes this convention, like in APL?</p>
  
  <p>Thanks for your help (I hope my question is clear despite my feeble grasp of both English and CSish...)</p>