Loading Python 2.7

[Seymore4Head]

When I installed Python, I installed 2.7 and 3.4.  I am using XP.
I have been using Python 3 by just right clicking on a py file and
choose Edit with Idle.  That works just fine when I am using 3, but
since I also use 2.7 for practice from online courses I haven't
figured out how to use the interactive shell.

What I do when I need to run 2.7 code is to just save the file to my
Python 2.7 folder and run a command prompt.  I then just type the py
file.  That works but I am left with a dos prompt when the file
finishes.  I sometimes would like to be able to use the interactive
shell with a 2.7 file in memory.

I don't know how to do that.