[Tutor] sys.path and the path order
davea at ieee.org
Fri Apr 23 10:23:30 CEST 2010
Garry Willgoose wrote:
> <div class="moz-text-flowed" style="font-family: -moz-fixed">My
> question is so simple I'm surprised I can't find an answer somewhere.
> I'm interested if I can rely on the order of the directories in the
> sys.path list. When I'm running a file from the comand line like
> python tellusim.py
> The string in entry sys.path appears to be the full path to the
> location of the file I'm running in this case tellusim ... i.e. it
> looks like '/Volumes/scone2/codes/tellusim0006'. This is good because
> for my code I need to create a search path for modules that is
> relative to the location of this file irrespective of the location I'm
> in when I invoke the script file (i.e. I could be in /Volumes/scone2
> and invoke it by 'python codes/tellusim0006/tellusim.py').
> The question is can I rely on entry  in sys.path always being the
> directory in which the original file resides (& across linux, OSX and
> Windows)? If not what is the reliable way of getting that information?
As Steven says, that's how it's documented.
There is another way, one that I like better. Each module, including
the startup script, has an attribute called __file__, which is the path
to the source file of that module.
Then I'd use os.path.abspath(), and os.path.dirname() to turn that into
an absolute path to the directory.
The only exception I know of to __file__ usefulness is modules that are
loaded from zip files. I don't know if the initial script can come from
a zip file, but if it does, the question changes.
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