The answer

samwyse samwyse at gmail.com
Mon Jan 18 13:28:51 CET 2010


On Jan 17, 8:30 pm, Jive Dadson <notonthe... at noisp.com> wrote:
> Okay, with your help I've figured it out.  Instructions are below, but
> read the caveat by Ben Fenny in this thread.  All this stuff is good for
> one default version of Python only.  The PYTHONPATH described below, for
> example, cannot specify a version number.  Yes, that's a pain in the
> butt, but there's no way around it.  If you switch versions, you may
> have to delete all the .pyc files that will show up in the module
> folders.  Python ought to check them to see if they are valid, but I do
> not know if it does so.
>
> These instructions are for MS Windows.
>
> 1) Create your modules folder. Let's say it's named "Modules."  The
> documentation calls it a "package."
>
> 2) In an explorer window or on the desktop, right click on My Computer,
> and select Properties.
>
> 3) Select the Advanced tab, and click on Environment Variables near the
> bottom.
>
> 4) Look for an environment variable named PYTHONPATH.
>
>     a) If you do not find one, create one using the New button(s). I
> don't know if it has to be in User Variables or System Variables.  To
> save time experimenting, I just put one in both. For the value, put the
> full path of the folder Modules.
>
>     b) If there's already a PYTHONPATH,  Edit it, adding a semi-colon
> and the full path of folder Module to the end.
>
> 5) Put your module folders into the folder Module.
>
> 6) (Here's a really arcane bit.) Into each module folder, put a file
> named __init__.py.  It will be executed when you load the module.  It
> can be empty, but it has to be there or else the module folder will be
> ignored.

In your original thread, you never quite said why you can't use site-
packages and .pth files.  Are you not allowed to modify your local
installation?  If you are writing something for distribution to
others, then site-packages and .pth files are the best way to go,
since they don't assume any particular operating system.  If you can't
(or won't) use them, then just create Module as a sub-directory of
wherever your program lives, since that directory is always prepended
to PYTHONPATH.  If you need to use the same module from multiple
directories, most modern operating systems support symbolic links; if
you're using Windows, well, here's a nickel kid, get yourself a better
computer (http://farm1.static.flickr.com/
89/240711122_f9888e5a3b_o.jpg).

I don't think that __init__.py is very arcane, since it is described
in detail in the documentation.  It's also a great place to use the
standard site.addsitedir() function, which is another platform
independent way to manipulate Python's search path.



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