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
If you do install Xcode you can get the latest and greatest open source libraries and packages. Consider using the excellent Mac Ports (http://www.macports.org) project. It is a package manager that will download source packages and their dependencies and build all the libraries and tools for you.
Installing Numpy becomes a one line command once Xcode and mac ports is installed:
sudo port install py27-numpy