If you are getting “`ipython: command not found`” when you try to run iPython at the command prompt, after you have installed it using:

sudo port install py27-ipython

(or whatever flavor of Python you prefer — I use 2.7 because that’s where support is most robust and newbs like me shouldn’t hang out on the bleeding edge), then what you need to do is to *select* it:

sudo port select –set ipython ipython27

Now, all better!