strange interaction between open and cwd

[Baz Walter]

On 03/05/10 14:18, Chris Rebert wrote:
> Whether or not /home/baz/tmp/xxx/ exists, we know from the very
> structure and properties of directory paths that its parent directory
> is, *by definition*, /home/baz/tmp/ (just chop off everything after
> the second-to-last slash). I would assume this is what happens
> internally.
> How exactly this interacts with, say, moving the directory to a new
> location rather than deleting it, I don't know; again, it would quite
> likely be platform-specific.

but how does '..' get resolved in the relative path '../abc.txt'? i'm 
assuming python must initially use getcwd() internally to do this, and 
then if that fails it falls back on something else. but what is that 
something else? is it something that is reproducible in pure python?