netCDF version 4 has many features not found in earlier versions of the
library and is implemented on top of HDF5. This module can read and
write files in both the new netCDF 4 and the old netCDF 3 format, and
can create files that are readable by HDF5 clients. The API modelled
after Scientific.IO.NetCDF, and should be familiar to users of that
module.

Many new features of netCDF 4 are implemented, such as multiple
unlimited dimensions, groups and zlib data compression. All the new
primitive data types (such as 64 bit and unsigned integer types) are
implemented, except variable-length strings (NC_STRING). User defined
data types (compound, vlen, enum etc.) are not supported.

WWW:  http://code.google.com/p/netcdf4-python/