>> an alternative standalone Python interpreter
>
> It's a convenient way to avoid having your standard library hijacked by registry keys installed by the regular interpreter.

Ah yes, that makes sense - it's maybe not the *right* way, but as a
practical approach it has benefits :-)

> However, if it detects "Lib\os.py" or "python36.zip" alongside the executable, it shouldn't look in the registry to figure out its home directory. That ought to be sufficient for portable cases, though of course there are some registry entries that will still have an impact (until 3.6.1, when we should be registry clean provided one of the landmark files is found).

And that of course is the "right" way - it's just taken a long time to
get there because of all the nastiness involved in interpreter startup
(see PEP 432 :-))

I'd forgotten (and hadn't gone and checked) that WinPython was
designed as a portable build.