> One of the places that the 'L' code *is* used is when parsing
> strange C types (like off_t)

It has unexepected consequences. Example:

   >>> x=open("x", "w")
   >>> x.seek(0.0)
   0.0
   >>> x.seek(-0.0)
   -0.0
   >>> x.seek(0.1)
   0.1
   >>> x.tell()
   0

I think that we should just raise an error in Python 3.2 because I consider this as a bug. It remembers me another bug related to file and float: http://bugs.python.org/issue5080#msg92400