How to create a netCDF file with python netCDF4?
11,132
This works:
from netCDF4 import Dataset
import numpy as np
root_grp = Dataset('py_netcdf4.nc', 'w', format='NETCDF4')
root_grp.description = 'Example simulation data'
ndim = 128 # Size of the matrix ndim*ndim
xdimension = 0.75
ydimension = 0.75
# dimensions
root_grp.createDimension('time', None)
root_grp.createDimension('x', ndim)
root_grp.createDimension('y', ndim)
# variables
time = root_grp.createVariable('time', 'f8', ('time',))
x = root_grp.createVariable('x', 'f4', ('x',))
y = root_grp.createVariable('y', 'f4', ('y',))
field = root_grp.createVariable('field', 'f8', ('time', 'x', 'y',))
# data
x_range = np.linspace(0, xdimension, ndim)
y_range = np.linspace(0, ydimension, ndim)
x[:] = x_range
y[:] = y_range
for i in range(5):
time[i] = i*50.0
field[i,:,:] = np.random.uniform(size=(len(x_range), len(y_range)))
root_grp.close()
The only difference is that I call the close()
method: root_grp.close()
.
Author by
Ohm
Updated on June 27, 2022Comments
-
Ohm about 2 years
I am learning how to use netCDF4 using Python module in Anaconda. I am trying to append values to two variables I have created
time
andfield
:from netCDF4 import Dataset import numpy as np root_grp = Dataset('py_netcdf4.nc', 'w', format='NETCDF4') root_grp.description = 'Example simulation data' ndim = 128 # Size of the matrix ndim*ndim xdimension = 0.75 ydimension = 0.75 # dimensions root_grp.createDimension('time', None) root_grp.createDimension('x', ndim) root_grp.createDimension('y', ndim) # variables time = root_grp.createVariable('time', 'f8', ('time',)) x = root_grp.createVariable('x', 'f4', ('x',)) y = root_grp.createVariable('y', 'f4', ('y',)) field = root_grp.createVariable('field', 'f8', ('time', 'x', 'y',)) # data x_range = np.linspace(0, xdimension, ndim) y_range = np.linspace(0, ydimension, ndim) x[:] = x_range y[:] = y_range for i in range(5): time[i] = i*50.0 field[i,:,:] = np.random.uniform(size=(len(x_range), len(y_range))) root_grp.close
But now when I print one of the variables I get that it's empty(!!):
Python 2.7.10 |Anaconda 2.4.1 (64-bit)| (default, Sep 15 2015, 14:50:01) [GCC 4.4.7 20120313 (Red Hat 4.4.7-1)] on linux2 Type "help", "copyright", "credits" or "license" for more information. Anaconda is brought to you by Continuum Analytics. Please check out: http://continuum.io/thanks and https://anaconda.org >>> from netCDF4 import Dataset >>> root_grp = Dataset('py_netcdf4.nc', 'r', format='NETCDF4') >>> print root_grp.variables["field"][:,:,:] [] >>>
What am I doing wrong here?
-
j08lue about 8 yearsTo avoid mistakes like that (e.g. missing brackets on
close
method), use the python with statement, like in this example.