[Bf-python] sitedirs and Python 2.4

[Ken Hughes]

Jonathan Merritt wrote:
> Hi Ken,
> 
> I should have read your email more carefully.  If I do the following 
> within Blender:
>    >>> import site
>    >>> site.main()
>    >>> import sys
>    >>> print sys.path
> then the site-packages directories *do* appear.  Without calling 
> site.main(), however, they don't appear:
>    >>> import site
>    >>> import sys
>    >>> print sys.path
> So, your patch will work at my end.
> 
> I still don't understand it though.
> 
> The source for site.py looks like it calls main() from the top level of 
> the file when it's imported.  Why should main() need to be called 
> separately?  Is this a known difference in behaviour in the embedded 
> interpreter compared with the normal command-line version?
> 
> Jonathan.
> 
> Jonathan Merritt wrote:
> 
>> The wierd thing is that when I do an:
>>    >>> import sys
>>    >>> print sys.path
>> from the native Python command-line interpreter, the site-packages 
>> directories are all present.  However, when I do the same thing from 
>> within Blender it doesn't include the site-packages!  They still 
>> aren't present even if I first manually "import site" within Blender, 
>> although "import site" raises no exceptions.

Here's what I can tell you from what I understand, but for any history 
of why things are done this way we'll have to ask Stephen and Willian. 
The internal interpreter relies on Py_Initialize() to load the sys and 
site modules.  The site module calculates the site-packages; how this is 
done changed between Python 2.3 and 2.4.  Python 2.3 built a list named 
"sitedirs" which the Blender interpreter accessed and appended to 
sys.path.  Python 2.4 now instead calculates what site-package 
directories to add to sys.path using a function addsitepackages().

I've played around some more this evening and first found that I could 
also add SOME of the site-packages to sys.path by getting a PyObject * 
for site.addsitepackages() and calling with PyObject_CallFunction(). 
But after I read the documentation on Py_Initialize() in the Python/C 
API Reference Manual:

   "The basic initialization function is Py_Initialize(). This
    initializes the table of loaded modules, and creates the
    fundamental modules __builtin__, __main__, sys, and exceptions.
    It also initializes the module search path (sys.path)."

 From this I tried *not* setting the system path after calling 
Py_Initialize() (there's a call to PySys_SetPath() in init_syspath).  I 
ended up with exactly the same site-packages in my sys.path as the 
python2.4 interpreter gave me (of course, the complete sys.path was 
different since Blender includes paths to its script directories).

Bottom line; maybe we're doing too much in our initialization code?

Ken