read netcdf

read netcdf#

Get variables from netcdf file

This module was written by Matthias Cuntz while at Department of Computational Hydrosystems, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany, and continued while at Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Nancy, France.

copyright:

Copyright 2009-2023 Matthias Cuntz, Stephan Thober, see AUTHORS.rst for details.

license:

MIT License, see LICENSE for details.

The following functions are provided

ncread(ncfile[, var, code, squeeze, ...])

Gets variables of a netcdf file

readnetcdf(*args, **kwargs)

Wrapper for ncread()
History

  • Written Jul 2009 by Matthias Cuntz (mc (at) macu (dot) de)

  • Removed quiet keyword, Jun 2012, Matthias Cuntz

  • Ported to Python 3, Feb 2013, Matthias Cuntz

  • Wrapper functions netcdfread, ncread, readnc, Oct 2013, Matthias Cuntz

  • overwrite keyword, Apr 2014, Stephan Thober

  • dims keyword, May 2014, Stephan Thober

  • attributes keyword, Jun 2016, Stephan Thober

  • Restrict overwrite to files with only one variables, Aug 2016, Stephan Thober

  • Do not count dimension variables in variable count for overwrite, Oct 2016, Matthias Cuntz

  • Remove wrappers netcdfread and readnc, Mar 2022, Matthias Cuntz

  • Remove reform keyword, Mar 2022, Matthias Cuntz

  • Put all info abilities into separate routine infonetcdf with wrapper function ncinfo, Mar 2022, Matthias Cuntz

  • Invert functions and wrapper functions, Feb 2023, Matthias Cuntz

  • Rename file to ncread, Nov 2023, Matthias Cuntz

  • Move ncinfo in separate file, Nov 2023, Matthias Cuntz

ncread(ncfile, var='', code=-1, squeeze=False, pointer=False, overwrite=False)[source]#

Gets variables of a netcdf file

Parameters:

  • ncfile (str) – netCDF file name

  • variables (bool, optional) – Get list of variables in ncfile

  • codes (bool, optional) – Get list of variable attributes code Missing codes will be filled with -1.

  • squeeze (bool, optional) – Squeeze output array, i.e. remove dimensions of size 1.

  • pointer (bool, optional) – Return pointers to the open file and to the variable if True, i.e. without actually reading the variable. The file will be open in read-only ‘r’ mode. overwrite precedes over pointer.

  • overwrite (bool, optional) – Return pointers to the open file and to the variable if True, where the file is opened in append ‘a’ mode allowing to modify the variable. ncread allows overwrite only if the file contains a single variable (without the dimension variables). overwrite precedes over pointer.

Returns:

  • numpy array of the variable with name *var or number code, or*

  • (file pointer, variable pointer)

Examples

Read variable or code

>>> ncfile = 'test_ncread.nc'
>>> print(ncread(ncfile, var='is1'))
[[1. 1. 1. 1.]
 [1. 1. 1. 1.]]
>>> print(ncread(ncfile, code=129))
[[2. 2. 2. 2.]
 [2. 2. 2. 2.]]

Just get file handle so that read is done later at indexing useful for example to inquire remote netcdf files first

>>> fh, var = ncread(ncfile, var='is1', pointer=True)
>>> print(var.shape)
(2, 4)
>>> print(var[:])
[[1. 1. 1. 1.]
 [1. 1. 1. 1.]]
>>> fh.close()

Change a variable in a file

>>> ncfile = 'test_ncread1.nc'
>>> print(ncread(ncfile, var='is1'))
[[1. 1. 1. 1.]
 [1. 1. 1. 1.]]
>>> fh, var = ncread(ncfile, var='is1', overwrite=True)
>>> var[:] *= 2.
>>> fh.close()
>>> print(ncread(ncfile, var='is1'))
[[2. 2. 2. 2.]
 [2. 2. 2. 2.]]
>>> fh, var = ncread(ncfile, var='is1', overwrite=True)
>>> var[:] *= 0.5
>>> fh.close()
readnetcdf(*args, **kwargs)[source]#

Wrapper for ncread()

Contents