Anders J. Munch wrote:
Another way is the strategy of "it's easier to ask forgiveness than to ask permission". If you replace: if(not os.path.isdir(zfdir)): os.makedirs(zfdir) with: try: os.makedirs(zfdir) except EnvironmentError: pass
then not only will your script become a micron more robust, but assuming zfdir typically does not exist, you will have saved the call to os.path.isdir.
... at the cost of an exception frame setup and an incomplete call to os.makedirs(). It's an open question whether the exception setup and recovery take less time than the call to isdir(), though I'd expect probably not. The exception route definitely makes more sense if the makedirs() call is likely to succeed; if it's likely to fail, then things are murkier.
Since isdir() *is* a disk i/o operation, then in this case the exception route is probably preferable anyhow. In either case, one must touch the disk; in the exception case, there will only ever be one disk access (which either succeeds or fails), while in the other case, there may be two disk accesses. However, if it wasn't for the extra disk i/o operation, then the 'if ...' might be slightly faster, even though the exception-based route is more Pythonic.
Jeff Shannon Technician/Programmer Credit International
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