[yt-users] Clear memory?

Hi, Is there any way in yt to get a script to delete (or ignore) all the .yt and .harray files and clear its memory? I run into errors when I'm re-doing a plot or I've re-run the simulation and over-written the last data set I looked at with yt. I have to exit yt, delete the above files by hand and restart, which is a bit of a pain. Elizabeth