Converting ascii file to netcdf using python

Question

I would like to add all the data from an ascii file to a netcdf file. The ascii file has data for every 0.25 degree cell on earth.

I am able to create all the lat/lon dimensions but not able to add the data. The ascii file is here: https://www.dropbox.com/s/lybu6yvm4ph7pcr/tmp.txt?dl=0

Can someone diagnose the code and see what is going wrong?

from netCDF4 import Dataset
import numpy, os, pdb, errno, sys

NUM_LATS = 180.0
NUM_LONS = 360.0

inp_dir  = 'C:\\Input\\'
out_dir  = 'C:\\Output\\nc\\'

def make_dir_if_missing(d):
    try:
        os.makedirs(d)
    except OSError as exception:
        if exception.errno != errno.EEXIST:
            raise

make_dir_if_missing(out_dir)

# Read ASCII File
fl_name  = inp_dir+'tmp.txt'
ascii_fl = numpy.loadtxt(fl_name, delimiter=' ')

# Compute dimensions of nc file based on # rows/cols in ascii file
fl_res   = NUM_LATS/ascii_fl.shape[0]
if fl_res != NUM_LONS/ascii_fl.shape[1]:
    print 'Incorrect dimensions in ascii file'
    sys.exit(0)

# Initialize nc file
out_nc   = out_dir+os.path.basename(inp_dir+'tmp.txt')[:-4]+'.nc'
nc_data  = Dataset(out_nc, 'w', format='NETCDF4')
nc_data.description = 'Test'

# dimensions
nc_data.createDimension('lat', ascii_fl.shape[0])
nc_data.createDimension('lon', ascii_fl.shape[1])
nc_data.createDimension('data', 1)

# Populate and output nc file
# variables
latitudes  = nc_data.createVariable('latitude', 'f4', ('lat',))
longitudes = nc_data.createVariable('longitude', 'f4', ('lon',))
glm_data   = nc_data.createVariable('glm_data', 'f4', ('lat', 'lon', 'data'), fill_value=-9999.0)

glm_data.units = ''

# set the variables we know first
latitudes  = numpy.arange(-90.5, 89.5, fl_res)
longitudes = numpy.arange(0.5, 360.5, fl_res)
glm_data   = ascii_fl  ### THIS LINE IS NOT WORKING!!!!!!!


nc_data.close()

N1B4 · Accepted Answer · 2015-07-25 19:46:43Z

2

You just need to explicitly write out the 2-dimensions for the variable glm_data:

glm_data[:,:] = ascii_fl[:,:]

answered Jul 25, 2015 at 19:46

N1B4

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3 Comments

N1B4 Over a year ago

Strange, it's OK on my end. What is not working for you?

user308827 Over a year ago

hmm, can you try opening it up in Panoply?

N1B4 Over a year ago

Yes, I'm able to view the data. If you use something like ncdump, can you see the data being written out OK to the file?

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