running python from the command line

running python from the command line

I am using mac os x, on which I thought a version of python was ready to go.
When I type "Python", I get the message "-bash: python: command not found".
If I look in the "Library" directory, I have a folder called "python" and
then there are 4 folders:
2.3
2.5
2.6
2.7
I have tried to google this and find how I can make any of the versions to
work, but I'm having trouble understanding the answers, because they seem
very specific to the poster.
I would be grateful if someone could tell me as simply as possible, what I
need to do to make the "python" command work. I want to learn how to do
things manually, so I don't want to use macports or whatever to do
everything for me.
Thank you.