Understanding .pth in site-packages

Philip Semanchuk philip at semanchuk.com
Sat Aug 27 19:18:38 CEST 2011

On Aug 27, 2011, at 12:56 PM, Josh English wrote:

> (This may be a shortened double post)
> I have a development version of a library in c:\dev\XmlDB\xmldb
> After testing the setup script I also have c:\python27\lib\site-packages\xmldb
> Now I'm continuing to develop it and simultaneously building an application with it.
> I thought I could plug into my site-packages directory a file called xmldb.pth with:
> c:\dev\XmlDB\xmldb
> which should redirect import statements to the development version of the library.
> This doesn't seem to work.

xmldb.pth should contain the directory that contains xmldb:

Examining sys.path at runtime probably would have helped you to debug the effect of your .pth file.

On another note, I don't know if the behavior of 'import xmldb' is defined when xmldb is present both as a directory in site-pacakges and also as a .pth file. You're essentially giving Python two choices from where to import xmldb, and I don't know which Python will choose. It may be arbitrary. I've looked for some sort of statement on this topic in the documentation, but haven't come across it yet. 

> Is there a better way to redirect import statements without messing with the system path or the PYTHONPATH variable?

Personally I have never used PYTHONPATH.

Hope this helps

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