Basically, if ~/lib/python is scanned before /usr/local/lib/python, it doesn't
matter if a system-wide installation has an older version installed as an
individual user can build their own version in their home directory; a user's
own binaries will then mask the system binaries for that user.

For example, I did "make install" or something similar to get libraries in
/usr/local. If Mercurial scanned my home directory before /usr/local, then when
I later did "make install-home", the libraries in ~/usr/libs would have been hit
before the global ones, whilst other users on the system could still use the old
version.

It basically saves me from having to set PYTHONPATH, but I don't know how
consistent distributions are with their home directory structures so it may not
be a sensible default setting. (I'm no Linux expert!)

Anyway, thanks very much for your time!