I need to install Numpy on my Mac OS X Lion 10.7. I googled a little bit, it seems like there are a lot of stuff needs to be installed. And some says I need install Xcode be
I have used a few software packages that require a fresh install of NumPy, that won't work with the built in NumPy or even with the built-in Python. The easiest way to install NumPy on the mac is to download any of these packages. This will work for most OS versions.
Still the other answers are valid, though this is a more general answer.
This is the SourceForge page of the project.