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From: Chris Kaynor <ckaynor@zindagigames.com>
Date: Mon, 24 Sep 2012 16:14:37 -0700
Subject: Re: python file API
To: Python <python-list@python.org>
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Xref: csiph.com comp.lang.python:29957

On Mon, Sep 24, 2012 at 3:37 PM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
> On Mon, Sep 24, 2012 at 4:14 PM, Chris Angelico <rosuav@gmail.com> wrote:
>> file.pos = 42 # Okay, you're at position 42
>> file.pos -= 10 # That should put you at position 32
>> foo = file.pos # Presumably foo is the integer 32
>> file.pos -= 100 # What should this do?
>
> Since ints are immutable, the language specifies that it should be the
> equivalent of "file.pos = file.pos - 100", so it should set the file
> pointer to 68 bytes before EOF.

There is no reason that it has to be an int object, however. It could
well return a "FilePosition" object which does not allow subtraction
to produce a negative result. Not saying its a good idea... Similarly,
it could be a more complex object with properties on it to determine
whether to seek from beginning or end.