A.1 Attribute Errors, Key Errors, Index Errors

Messages starting ``AttributeError:'', ``KeyError:'' or ``IndexError:'' generally indicate you were trying to reference or manipulate part of a multi-element variable (lists and arrays) but that element didn't exist. For example:

  >>> xx = array([1,2])
  >>> print xx[5]
  Traceback (most recent call last):
    File "<pyshell#9>", line 1, in ?
      print xx[5
  IndexError: index out of bounds