changing sys.path
Steven D'Aprano
steve+comp.lang.python at pearwood.info
Wed Feb 1 19:51:34 EST 2012
On Wed, 01 Feb 2012 17:47:22 +0000, Andrea Crotti wrote:
> Yes they are exactly the same, because in that file I just write exactly
> the same list,
> but when modifying it at run-time it doesn't work, while if at the
> application start
> there is this file everything works correctly...
>
> That's what really puzzles me.. What could that be then?
Are you using IDLE or WingIDE or some other IDE which may not be
honouring sys.path? If so, that's a BAD bug in the IDE.
Are you changing the working directory manually, by calling os.chdir? If
so, that could be interfering with the import somehow. It shouldn't, but
you never know...
Are you adding absolute paths or relative paths?
You say that you get an ImportError, but that covers a lot of things
going wrong. Here's a story. Could it be correct? I can't tell because
you haven't posted the traceback.
When you set site-packages/my_paths.pth you get a sys path that looks
like ['a', 'b', 'fe', 'fi', 'fo', 'fum']. You then call "import spam"
which locates b/spam.py and everything works.
But when you call sys.path.extend(['a', 'b']) you get a path that looks
like ['fe', 'fi', 'fo', 'fum', 'a', 'b']. Calling "import spam" locates
some left over junk file, fi/spam.py or fi/spam.pyc, which doesn't
import, and you get an ImportError.
--
Steven
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