How do I launch 'somewhere/Sweety.py' without 'somewhere/'?

[Martin Bless]

Working in dos boxes of win - but probably independent of this here's
my question:

ok,   PYTHON   starts Python
ok,   PYTHON   c:\really\long\path\somewhere\Sweety.py
executes  my beloved script Sweety.py.

How can I start   Sweety.py   without having to specify that awful
long path?

Martin