[netCDF #VKP-631083]: error modifying existing attribute

Jeff,

> Russ/Dennis:  I've filed two tickets on support-netcdf,  I think they 
> both represent bugs in 4.2rc1.  I hope you can find the time to take a 
> look at them before 4.2 is released.  One (netCDF #VKP-631083) has to do 
> with changing an existing attribute in a netcdf4 file, and the other 
> (netCDF #XHX-254015) is a regression from 4.1.3 that occurs when trying 
> to read opendap aggregation datasets.

Thanks, Jeff, I've reproduced the bug in a C program.  You can monitor this 
Jira issue to see when it's fixed:

  https://www.unidata.ucar.edu/jira/browse/NCF-156

Thanks for reporting the bug and providing a reproducible example program.

--Russ

> If I open a NETCDF4 file in "append" mode and immediately try to modify
> an existing attribute, I get this error
> 
> NetCDF: Operation not allowed in data mode
> 
> However, if I first create a new attribute, before trying to modify an
> existing one, all is well.  Here is a python script that triggers the
> error with netcdf 4.1.3/hdf5 1.8.8
> 
> from netCDF4 import Dataset
> f = Dataset('pv.nc','w')
> lat = f.createDimension('lat',181)
> lon = f.createDimension('lon',360)
> lev = f.createDimension('lev',60)
> pv = f.createVariable('PV','f',('lev','lat','lon'),fill_value=-999)
> pv.units="K m**2 kg**-1 s**-1"
> pv.longname = 'Potential Vorticity'
> f.close()
> f = Dataset('pv.nc','a')
> pv = f.variables['PV']
> pv.longname = 'Ertel Potential Vorticity'  ==> error occurs here
> f.close()
> 
> Here is the workaround:
> 
> pv.testatt = 'test'
> pv.longname = 'Ertel Potential Vorticity'
> del pv.testatt
> f.close()
> 
> I can create a C program to trigger the error if you like.
> 
> Regards,
> 
> Jeff
> 
> 
> 

Russ Rew                                         UCAR Unidata Program
address@hidden                      http://www.unidata.ucar.edu



Ticket Details
===================
Ticket ID: VKP-631083
Department: Support netCDF
Priority: Urgent
Status: Closed