In article <4b3dcfab.3030...@v.loewis.de>, Martin v. Loewis <mar...@v.loewis.de> wrote: > >Notice that in cases where the failure may be expected, Python >also offers variants that avoid the exception: >- if you look into a dictionary, expecting that a key may not > be there, a regular access, d[k], may give a KeyError. However, > alternatively, you can use d.get(k, default) which raises no > exception, and you can test "k in d" in advance. >- if you open a file, not knowing whether it will be there, > you get an IOError. However, you can use os.path.exists in > advance to determine whether the file is present (and create > it if it's not).
But you *still* need to catch IOError: someone might delete the file after the test. Figuring out how to deal with race conditions is one of the main reasons Alex Martelli advocates EAFP over LBYL. Of course, in the real world, you often end up wanting to do it both ways. -- Aahz (a...@pythoncraft.com) <*> http://www.pythoncraft.com/ Weinberg's Second Law: If builders built buildings the way programmers wrote programs, then the first woodpecker that came along would destroy civilization. -- http://mail.python.org/mailman/listinfo/python-list
