PyNIO is a Python package that allows read and/or write access to a variety of data formats using an interface modeled on netCDF. PyNIO is composed of a C library called libnio along with a Python module based on and with an interface similar to the Scientific.IO.NetCDF module written by Konrad Hinsen. The C library contains the same data I/O code used in NCL, a scripting language developed for analysis and visualization of geo-scientific data. Currently supported formats include: * netCDF (read/write) * GRIB 1 and GRIB 2 (read-only) * HDF 4 (read/write for Scientific DataSets only) * HDFEOS 2 (read-only for Grid and Swath data only) * CCM history files (read-only)