how to run python-script from the python promt? [absolute newbie]

[nukeymusic]

How can I load a python-script after starting python in the
interactive mode?
I tried with
>>>load 'myscript.py'
>>>myscript.py
>>>myscript

but none of these works, so the only way I could work further until
now was copy/paste line per line of my python-script to the
interactive mode prompt
I do know how to run the script non-interactively, but what I want to
do is adding lines to the code I have written thus far in interactive
mode.

thanks in advance
nukey