Idea: PYTHONPATH_VER

[Peter Hansen]

Fernando Perez wrote:

> Peter Hansen wrote:
>>Having missed the discussion preceding, I'm probably off the mark,
>>but in my experience just about everything that can be solved with
>>PYTHONPATH can be handled with a .pth file as well, and I haven't
>>had any need to use PYTHONPATH for quite some time as a result.
> 
> How do you handle the fact that .pth files are only read from certain places,
> and not others?  This problem has me currently rather stuck with gross hacks: 

I confess to never having had any particular troubles with it, other
than in trying to use it for adding special other directories during
unit testing, where I had to do "import site; site.addsitedir('.')"
or something close to that at the top of my xxx_test.py file.

> packages like Numeric, which rely on a .pth file instead of being a 'true'
> python package (with __init__.py), are very problematic.  

Sorry, haven't used it.

> --home=/usr/local'.  The problem is that python does NOT scan this directory
> for .pth files, even if it is listed in PYTHONPATH.  .pth files only have an
> effect for directories in sys.prefix, I think.

Actually, I believe it's recursive, in that any directories added during
.pth processing are themselves scanned for .pth files and the new ones
added, and so on.

> I have actually come to HATE with a vengeance packages which rely on .pth files,
> because of this behavior of python of not including them for anything in
> PYTHONPATH.  So I would really appreciate pointers from someone who has
> successfully solved this, since it's quite likely that I'm just misusing the
> system.

I'm not sure I've seen a package which *relied* on it, except for
pywin32, and it seems to work very nicely and the .pth file (which
I just had to verify is still there) is pretty much invisible.

I might have some better idea how to deal with it if I'd ever had
trouble with it.  One thing to note: I do most development on Windows.
Perhaps, for some reason, the problems are lesser there.  (Which would
be a little surprising, but given Linux' issues with installing
software, perhaps not entirely unlikely.)

-Peter