NumPy is a requirement to work with PyTables. This is the second step in the install process, after getting HDF5 set up. These instructions are based on the ones found on the NumPy site, but I’m summarizing things for my own use later on. First, you’ll need to install the Fortran compiler for OSX (gFortran). Fortunately there’s a Fortran universal binary installer. Next, get the NumPy source. You can find it on Sourceforge.