You raise a valid point: that by abstracting the file pointer into a position attribute you risk "de-coupling" the conceptual link between the underlying file and your abstraction in the python interpreter, but I think the programmer can take responsibility for maintaining the abstraction.
The key possible fault will be whether you can trap (OS-level) exceptions when assigning to the pos attribute beyond the bounds of the actual file on the system... markj -- http://mail.python.org/mailman/listinfo/python-list
