NumPy is a package that defines a multi-dimensional array object and associated fast math functions that operate on it. It also provides simple routines for linear algebra and fft and sophisticated random-number generation. NumPy replaces both Numeric and Numarray. http://www.scipy.org and http://numeric.scipy.org
A very complete manual by the principal author of Numpy, Travis Oliphant, is available for free (although donations are accepted). Note that the online documentation via docstring is rather complete and not stripped in any way. The manual for Numpy's predecessor Numeric is mostly still valid and freely available from here or here. Further documentation is available from http://www.scipy.org/Documentation