The following packages are required to work with ESMPy:

The following packages are optional:

  • ESMF installation with NetCDF - required to create Grids and Meshes from file
    • NetCDF must be built as a shared library for ESMPy installation to succeed

  • mpi4py- python bindings to MPI, needed to run some of the parallel regridding examples

  • nose - for nose testing

Getting the code

The ESMPy source code can be downloaded from the ESMF git repository.

The ESMF User’s Guide contains information on building and installing ESMF.

The ESMF Reference Manual contains information on the architecture of ESMF, example code, and details of the API (Application Programming Interface).

Anaconda Packages

ESMPy conda packages are available through the conda-forge channel:

conda create -n esmpy -c conda-forge esmpy

Specific versions of the conda package can be installed like this:

conda create -n esmpy -c conda-forge esmpy=8.1.0

Development versions can be found in the esmpy_dev channel:

conda create -n esmpy -c conda-forge -c esmpy_dev esmpy

Installing ESMPy from Source

When installing from source, ESMPy requires a pointer to a file named that is generated during an ESMF installation. The path of this file is:


If the ESMFMKFILE flag is set when building ESMPy then it will not need to be referenced again. If not, an environment variable of the same name must be set with the path to the file every time a new shell is initiated.

ESMPy can be installed in a custom location using the --prefix, --home, or --install-base flags to the install command. If this is done, then this location needs to be added to the PYTHONPATH environment variable every time a new shell is initiated. If a custom install location is not specified, ESMPy will be installed in the standard Python package installation directory on that particular machine.

An installation of ESMPy in the default location for Python packages can be done with the following command issued from the top level ESMPy directory:

python build --ESMFMKFILE=<>/ install
  • custom install location:

python build --ESMFMKFILE=<>/

python install --prefix=<custom_install_location>

setenv PYTHONPATH <custom_install_location>/lib/\*/site_packages

Please contact with any questions.

Importing ESMPy

To use ESMPy in an external program, import it with:

import ESMF


The ESMPy testing is done with the nose package, both in serial and parallel. The nose commands are wrapped in the following ESMPy targets:

python test

python test_examples

python test_regrid_from_file

python test_parallel

python test_examples_parallel

python test_regrid_from_file_parallel


The regrid_from_file tests can take up a lot of memory and bandwidth. The test_regrid_from_file_dryrun command will simply download the test files without actually running them (allowing the stress on the machine to be applied to bandwidth first, and then memory).

Alternatively, individual tests can be run with nose using the following format:

nosetests <file>:<test>


nosetests src/ESMF/test/test_api/


ESMPy doesn’t include many aspects of ESMF, including components, field bundles, time management, etc. The limitations listed here are relative to ESMF offline and integrated regridding capabilities.

  • ESMPy cannot use an ESMF installation that is built with external LAPACK support.

  • Coordinates cannot be retrieved from the elements of a Mesh. This can affect the ability to set Field values on a source Mesh created from file when using conservative regridding.

  • Multi-tile Grid support is limited to cubed-sphere grids created on 6 processors. A cubed-sphere grid can be created on any number of processors, but only when it is created on 6 processors will the coordinates be retrievable for the entire object. A Field created from a cubed-sphere Grid cannot be written to file in parallel.

  • There is no FieldBundle class, only single Fields.

Testing related:

  • Nightly regression testing is limited to a small subset of the ESMF test platforms, including Darwin and Linux running gfortran with openMPI.