problem with netCDF4 OpenDAP

Tom P werotizy at freent.dd
Fri Aug 14 09:18:54 CEST 2015


On 08/13/2015 05:55 PM, Jason Swails wrote:
>
>
> On Thu, Aug 13, 2015 at 6:32 AM, Tom P <werotizy at freent.dd
> <mailto:werotizy at freent.dd>> wrote:
>
>     I'm having a problem trying to access OpenDAP files using netCDF4.
>     The netCDF4 is installed from the Anaconda package. According to
>     their changelog, openDAP is supposed to be supported.
>
>     netCDF4.__version__
>     Out[7]:
>     '1.1.8'
>
>     Here's some code:
>
>     url =
>     'http://www1.ncdc.noaa.gov/pub/data/cmb/ersst/v3b/netcdf/ersst.201507.nc'
>     nc = netCDF4.Dataset(url)
>
>     I get the error -
>     netCDF4/_netCDF4.pyx in netCDF4._netCDF4.Dataset.__init__
>     (netCDF4/_netCDF4.c:9551)()
>
>     RuntimeError: NetCDF: file not found
>
>
>     However if I download the same file, it works -
>     url = '/home/tom/Downloads/ersst.201507.nc <http://ersst.201507.nc>'
>     nc = netCDF4.Dataset(url)
>     print nc
>       . . . .
>
>     Is it something I'm doing wrong?
>
>
> ​Yes.  URLs are not files and cannot be opened like normal files.
>   netCDF4 *requires* a local file as far as I can tell.
>
> All the best,
> Jason
>
> --
> Jason M. Swails
> BioMaPS,
> Rutgers University
> Postdoctoral Researcher

Thanks for the reply but that is not what the documentation says.

http://unidata.github.io/netcdf4-python/#section8
"Remote OPeNDAP-hosted datasets can be accessed for reading over http if 
a URL is provided to the netCDF4.Dataset constructor instead of a 
filename. However, this requires that the netCDF library be built with 
OPenDAP support, via the --enable-dap configure option (added in version 
4.0.1)."

and for the Anaconda package -
http://docs.continuum.io/anaconda/changelog
"2013-05-08: 1.5.0:
Highlights:
   updates to all important packages: python, numpy, scipy, ipython, 
matplotlib, pandas, cython
   added netCDF4 (with OpenDAP support) on Linux and MacOSX"



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