ncompare 1.1.1

Compare the structure of two NetCDF files at the command line

ncompare

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Compare the structure of two NetCDF files at the command line. ncompare generates a view of the matching and non-matching groups and variables between two NetCDF datasets.

Installing

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Using pip

Install the latest version of the package from PyPI using pip:

pip install ncompare

Other methods:

For local development, one can clone the repository and then use poetry or pip from the local directory:

git clone https://github.com/nasa/ncompare.git

(Option A) using poetry:

ii) Follow the instructions for installing poetry here.

iii) Run poetry install from the repository directory.

(Option B) using pip:

ii) Run pip install . from the repository directory.

Usage

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ncompare <netcdf file #1> <netcdf file #2>

For example:

ncompare S001G01.nc S001G01_SUBSET.nc -g product -v ozone_profile --report subset_comparison.txt

Or, If installed using a poetry environment:

poetry run ncompare <netcdf file #1> <netcdf file #2>

Options

• --file-text [FILE_PATH]: Text file to write output to.
• --file-csv [FILE_PATH]: Comma separated values (CSV) file to write output to.
• --file-xlsx [FILE_PATH]: Excel file to write output to.
• --no-color : Turn off all colorized output.
• --show-attributes : Include variable attributes in the table that compares variables.
• --show-chunks : Include chunk sizes in the table that compares variables.
• -v (--comparison_var_name) [VAR_NAME]: Compare specific values for this variable.
• -g (--comparison_var_group) [VAR_GROUP]: Group that contains the comparison_var_name.

How to test ncompare locally

If installed using a poetry environment, the tests can be run with:

poetry run pytest tests

Motivation

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The cdo (climate data operators) tool does not support NetCDF4 groups. Moreover, nco operators' ncdiff function computes value differences, but --- as far as the developers of this tool are aware --- nco does not have a simple function to show structural differences between NetCDF4 datasets. Note that h5diff, provided in the HDF5 software, can also be used to find differences. In comparison to h5diff, ncompare is written and runnable in Python; ncompare provides aligned and colorized difference report for quicker assessments of groups, variable names, types, shapes, and attributes; and can generate report files formatted for other applications. However, note that h5diff provides comparison of some otherwise "hidden" hdf5 properties, such as _Netcdf4Dimid or _Netcdf4Coordinates, which are not currently assessed by ncompare.

Known limitations

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• ncompare uses xarray to access the root-level dimensions. In some cases, xarray will miss dimensions whose names do not also exist as variable names in the dataset (also known as non-coordinate dimensions).
• Some underlying HDF5 properties, such as _Netcdf4Dimid or _Netcdf4Coordinates, are not currently assesssed by ncompare.

Notices:

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Copyright 2023 United States Government as represented by the Administrator of the National Aeronautics and Space Administration. All Rights Reserved.

Third-Party Software:

This software calls the following third-party software, which is subject to the terms and conditions of its licensor, as applicable at the time of licensing. Third-party software is not bundled with this software, but may be available from the licensor.

License hyperlinks are provided here for information purposes only:

item	license	link
colorama	BSD-3-Clause	https://opensource.org/licenses/BSD-3-Clause
netCDF4	MIT License	https://opensource.org/licenses/MIT
numpy	BSD-3-Clause	https://opensource.org/licenses/BSD-3-Clause
openpyxl	MIT License	https://opensource.org/licenses/MIT
xarray	Apache License, version 2.0	https://www.apache.org/licenses/LICENSE-2.0
Python	Standard Library Python Software Foundation (PSF) License Agreement	https://docs.python.org/3/license.html#psf-licenseDisclaimers

No Warranty:

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