def Quartiles( key, numbers ):
  """
  This function identifies the 0, 25, 50, 75 and 100 percentile elements in 
  the list of number (which must be sorted).  The elements are returned in 
  a dictionary whose keys are given by the key (three letter acroymn) with
  the percentile string substituted.
  If numbers contains less than 5 elements it retuns a dictionary with all values
  equal to int(0).
  """

  numbers.sort();
  l = (len(numbers)-1)/4.0;
  if l < 0:
    return { key%0   :0,
             key%25  :0,
             key%50  :0,
             key%75  :0,
             key%100 :0 };
  quartiles = { key % (q*25,): numbers[int(q*l)] for q in range(0,5) };

  return quartiles;