Detect existing files?

Michael Hudson mwh at python.net
Wed May 2 20:10:46 CEST 2001


Stephan Schulz <schulz at informatik.tu-muenchen.de> writes:

> I need the opposite case - if the file exists, I leave it alone,
> otherwise I create it. 

Then you want something along the lines of

os.fdopen(os.open(filepath, os.O_RDWR|os.O_CREAT|os.O_EXCL, 0700), "r+w")

you *don't* want to test if the file exists and then call open, 'cause
then you have a race condition.

If you're creating temporary files, you want to use tempfile in the
standard library. which contains much cleverness intended to get it
right.

> Moreover, I'm not yet into exception handling.

Here, you don't really have a choice.  But relax; it's easy.

Cheers,
M.

-- 
  In case you're not a computer person, I should probably point out
  that "Real Soon Now" is a technical term meaning "sometime before
  the heat-death of the universe, maybe".
                                     -- Scott Fahlman <sef at cs.cmu.edu>



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