Netcdf4 for Python successful save, failed to visualize

Question

I am having a hard time when I want to add new groups on a existing netcdf file with python. MWE works on my machine.

MWE

import os 
import numpy as np
from scipy.io import netcdf
from netCDF4 import Dataset

try:
    os.remove('test.nc')
except OSError:
    pass

mydata = np.linspace(1,30,30)

g=Dataset('test.nc','w',format='NETCDF4') 
g.description = 'The data in this file was created for a test'
g.close()

#Do stuff

g=Dataset('test.nc','r+',format='NETCDF4') 
g1 = g.createGroup('grp1')
g1.createDimension('dim', len(mydata))
ncdata = g1.createVariable('data1', 'f8', ('dim',)); ncdata[:] = mydata
ncdata = g1.createVariable('data2', 'f8', ('dim',)); ncdata[:] = mydata
g.close()


#Do stuff

g=Dataset('test.nc','r+',format='NETCDF4') 
g1 = g.createGroup('grp2')
g1.createDimension('dim', len(mydata))
ncdata = g1.createVariable('data1', 'f8', ('dim',)); ncdata[:] = mydata
ncdata = g1.createVariable('data2', 'f8', ('dim',)); ncdata[:] = mydata
g.close()

However I can't open my file with ncview , instead I get that

Ncview 1.93g David W. Pierce 24 February 2009 http://meteora.ucsd.edu:80/~pierce/ncview_home_page.html Copyright (C) 1993 through 2009, David W. Pierce Ncview comes with ABSOLUTELY NO WARRANTY; for details type ncview -w'. This is free software licensed under the Gnu General Public License version 3; type ncview -w'. This is free software licensed under the Gnu General Public License version 3; type ncview -w'. This is free software licensed under the Gnu General Public License version 3; type ncview -c' for redistribution details.

no displayable variables found!

It says no displayable variables found! , but via ncdump -h test.nc I am able to see the following lines;

netcdf test {

// global attributes: :description = "The data in this file was created for a test" ;

group: grp1 { dimensions: dim = 30 ; variables: double data1(dim) ; double data2(dim) ; } // group grp1

group: grp2 { dimensions: dim = 30 ; variables: double data1(dim) ; double data2(dim) ; } // group grp2 }

Am I missing something in my Python script? (I am thinking ncview is okay cause I am able to see very same data when I do not save them inside a netcdf group )

Answer 1

You might try upgrading your ncview version; 1.93g is pretty old. 2.1.6 (released fall 2015) is available here: http://meteora.ucsd.edu/~pierce/ncview_home_page.html