Can I have both Python 2.7 and Python 3.1 at the same time on the Mac?

[Bill Felton]

Hi All,
I'm new to python, trying to learn it from a variety of resources, including references posted recently to this list.
I'm going through /www.openbookproject.net/thinkCSpy/ and find it makes use of gasp, which apparently is not compatible with 3.1.
I've also seen various resources indicate that one can install both Python 2.7 and Python 3.1 -- but when I did this, I get no end of problems in the 2.7 install.  IDLE, in particular, fails rather spectacularly, even if I launch it directly from the Python 2.7 directory in which it resides.
So, either I've been misled and should only try to have one or the other.  OR I'm missing some (probably simple) step that's mucking me up.
Help?

Thanks,
Bill