[Python-Dev] UserString
Barry Warsaw
barry at python.org
Tue Feb 22 03:50:01 CET 2005
On Mon, 2005-02-21 at 11:15, Guido van Rossum wrote:
> Right. There are plenty of examples where LBYL is better, e.g. because
> there are too many different exceptions to catch, or they occur in too
> many places. One of my favorites is creating a directory if it doesn't
> already exist; I always use this LBYL-ish pattern:
>
> if not os.path.exists(dn):
> try:
> os.makedirs(dn)
> except os.error, err:
> ...log the error...
>
> because the specific exception for "it already exists" is quite subtle
> to pull out of the os.error structure.
Really? I do this kind of thing all the time:
import os
import errno
try:
os.makedirs(dn)
except OSError, e:
if e.errno <> errno.EEXIST:
raise
-Barry
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