How python knows where non standard libraries are stored ?

[dieter]

ast <none at gmail.com> writes:
> I looked for windows environment variables to tell python
> how to fill sys.path at startup but I didn't found.
>
> So how does it work ?

Read the (so called) docstring at the beginning of the module
"site.py".

Either locate the module source in the file system
and read it in an editor
or in an interactive Python do:

   import site
   help(site)