Check for presence fo directory

[Peter Hansen]

Maurice LING wrote:
> 
>> Should we assume you're rejecting os.path.exists() for some reason?
>>
> You can assume Maurice.knowledge(os.path.exists()) to raise an 
> exception. Thanks, I guess os.path.exists() is the one to use.

Make sure you check out its siblings, os.path.isfile() and
os.path.isdir(), as well.  Often it can be important to
make sure you aren't accidentally trying to treat an
*existing* file as a directory.

-Peter