[netcdfgroup] Unexpectedly large netCDF4 files from python

• To: netcdfgroup@xxxxxxxxxxxxxxxx
• Subject: [netcdfgroup] Unexpectedly large netCDF4 files from python
• From: Val Schmidt <vschmidt@xxxxxxxxxxxx>
• Date: Tue, 5 Apr 2016 14:44:42 -0400

Hello netcdf folks,

I’m testing some python code for writing sets of timestamps and variable length 
binary blobs to a netcdf file and the resulting file size is perplexing to me. 

The following segment of python code creates a file with just two variables, 
“timestamp” and “data”, populates the first entry of the timestamp variable 
with a float and the corresponding first entry of the data variable with an 
array of 100 unsigned 8-bit integers. The total amount of data is 108 bytes. 

But the resulting file is over 73 MB in size. Does anyone know why this might 
be so large and what I might be doing to cause it?

Thanks,

Val


from netCDF4 import Dataset
import numpy

f = Dataset('scratch/text3.nc','w')

dim = f.createDimension('timestamp_dim',None)
data_dim = f.createDimension('data_dim',None)

data_t = f.createVLType('u1','variable_data_t’)

timestamp = f.createVariable('timestamp','d','timestamp_dim')
data = f.createVariable('data',data_t,'data_dim’)

timestamp[0] = time.time()
data[0] = uint8( numpy.ones(1,100))

f.close()

------------------------------------------------------
Val Schmidt
CCOM/JHC
University of New Hampshire
Chase Ocean Engineering Lab
24 Colovos Road
Durham, NH 03824
e: vschmidt [AT] ccom.unh.edu
m: 614.286.3726

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