It doesn't seem like there's a meaningful functional difference between try/except and isfile(), so you should use which one makes sense.
If you want to read a file, if it exists, do
try: f = open(filepath)except IOError: print 'Oh dear.'But if you just wanted to rename a file if it exists, and therefore don't need to open it, do
if os.path.isfile(filepath): os.rename(filepath, filepath +'.old')If you want to write to a file, if it doesn't exist, do
# python 2if not os.path.isfile(filepath): f = open(filepath, 'w')# python 3, x opens for exclusive creation, failing if the file already existstry: f = open(filepath, 'wx')except IOError: print 'file already exists'If you need file locking, that's a different matter.
