Make xESMF optional

.github/workflows/main.yml

@@ -52,24 +52,23 @@ jobs:
           python -m tox -e lint
 
   test-pypi:
-    name: Test with Python${{ matrix.python-version }} (PyPI/tox)
+    name: Test with Python${{ matrix.python-version }} (PyPI/tox, no ESMF)
     needs: lint
     runs-on: ubuntu-latest
     env:
       COVERALLS_PARALLEL: true
       COVERALLS_SERVICE_NAME: github
-      esmf-version: 8.4.2
     strategy:
       matrix:
         include:
           - python-version: "3.9"
-            tox-build: "py39-esmpy-coveralls"
+            tox-build: "py39-coveralls"
           - python-version: "3.10"
-            tox-build: "py310-esmpy-coveralls"
+            tox-build: "py310-coveralls"
           - python-version: "3.11"
-            tox-build: "py311-esmpy-coveralls"
+            tox-build: "py311-coveralls"
 #          - python-version: "3.12"
-#            tox-build: "py312-esmpy-coveralls"
+#            tox-build: "py312-coveralls"
     defaults:
       run:
         shell: bash -l {0}
@@ -79,21 +78,17 @@ jobs:
         with:
           egress-policy: audit
       - uses: actions/checkout@v4.1.1
-      - name: Setup Conda (Micromamba) with Python ${{ matrix.python-version }}
-        uses: mamba-org/setup-micromamba@v1.8.0
+      - name: Set up Python${{ matrix.python-version }}
+        uses: actions/setup-python@0a5c61591373683505ea898e09a3ea4f39ef2b9c # v5.0.0
         with:
-          cache-downloads: true
-          environment-name: xscen-pypi
-          create-args: >-
-            esmf=${{ env.esmf-version }}
-            mamba
-            python=${{ matrix.python-version }}
-            tox
+          python-version: ${{ matrix.python-version }}
+      - name: Install tox
+        run: |
+          python -m pip install tox~=4.0
       - name: Test with tox
         run: |
           python -m tox -e ${{ matrix.tox-build }}
         env:
-          ESMF_VERSION: ${{ env.esmf-version }}
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           COVERALLS_FLAG_NAME: run-Python${{ matrix.python-version }}
 

CHANGES.rst

@@ -10,6 +10,7 @@ New features and enhancements
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 * Added a new argument ``indicators_kw`` to ``xs.ensembles.build_partition_data``. (:pull:`315`).
 * `xscen` is `Semantic Versioning 2.0.0 <https://semver.org/spec/v2.0.0.html>`_ compliant. (:pull:`319`).
+* `xesmf` made an optional dependency, making `xscen` easier to install with `pip`. (:pull:`337`).
 
 Internal changes
 ^^^^^^^^^^^^^^^^

pyproject.toml

@@ -64,7 +64,6 @@ dependencies = [
   "toolz",
   "xarray<2023.11.0", # FIXME: Remove when pandas 2.2 is released and xclim is fixed.
   "xclim>=0.46.0",
-  "xesmf>=0.7",
   "zarr"
 ]
 
@@ -105,6 +104,9 @@ docs = [
   "sphinx-rtd-theme>=1.0",
   "sphinxcontrib-napoleon"
 ]
+extra = [
+  "xesmf>=0.7"
+]
 
 [project.urls]
 "About Ouranos" = "https://www.ouranos.ca/en/"

tests/test_aggregate.py

@@ -8,6 +8,11 @@
 import xscen as xs
 from xscen.testing import datablock_3d
 
+try:
+    import xesmf as xe
+except ImportError:
+    xe = None
+
 
 class TestClimatologicalMean:
     def test_future_warning(self):
@@ -414,6 +419,8 @@ class TestSpatialMean:
     )
     @pytest.mark.parametrize("lonstart", [-70, -30, 0])
     def test_global(self, lonstart, method, exp):
+        if method == "xesmf" and xe is None:
+            pytest.skip("xesmf needed for testing averaging with method xesmf")
         ds = datablock_3d(
             np.array([[[0, 1, 2], [1, 2, 3], [2, 3, 4]]] * 3, "float"),
             "tas",

tests/test_ensembles.py

@@ -5,7 +5,11 @@
 import pytest
 import xarray as xr
 import xclim as xc
-import xesmf
+
+try:
+    import xesmf as xe
+except ImportError:
+    xe = None
 from xclim.testing.helpers import test_timeseries as timeseries
 
 import xscen as xs
@@ -1064,6 +1068,7 @@ def test_attribute_weight_error(self):
 
 
 class TestEnsemblePartition:
+    @pytest.mark.skipif(xe is None, reason="xesmf needed for testing regrdding")
     def test_build_partition_data(self, samplecat, tmp_path):
         # test subset
         datasets = samplecat.search(variable="tas").to_dataset_dict(
@@ -1083,7 +1088,7 @@ def test_build_partition_data(self, samplecat, tmp_path):
         assert [i for i in ds.data_vars] == ["tg_mean"]
 
         # test regrid
-        ds_grid = xesmf.util.cf_grid_2d(-75, -74, 0.25, 45, 48, 0.55)
+        ds_grid = xe.util.cf_grid_2d(-75, -74, 0.25, 45, 48, 0.55)
         datasets = samplecat.search(variable="tas", member="r1i1p1f1").to_dataset_dict(
             xarray_open_kwargs={"engine": "h5netcdf"}
         )

tests/test_regrid.py

@@ -1,5 +1,10 @@
 import numpy as np
+import pytest
 
+try:
+    import xesmf as xe
+except ImportError:
+    xe = None
 from xscen.regrid import create_bounds_rotated_pole, regrid_dataset
 from xscen.testing import datablock_3d
 
@@ -22,6 +27,7 @@ def test_create_bounds_rotated_pole():
     np.testing.assert_allclose(bnds.lat_bounds[-1, -1, 1], 42.5)
 
 
+@pytest.mark.skipif(xe is None, reason="xesmf needed for testing regrdding")
 class TestRegridDataset:
     def test_simple(self, tmp_path):
         dsout = datablock_3d(

tox.ini

@@ -2,7 +2,7 @@
 min_version = 4.0
 envlist =
     lint
-    py{39,310,311,312}-esmpy
+    py{39,310,311,312}
     docs-esmpy
 requires =
     babel
@@ -55,30 +55,19 @@ commands =
     pytest --xdoctest xscen --durations=10 {posargs}
 
 [testenv]
-description = Run tests with pytest under {basepython} (Anaconda distribution)
+description = Run tests with pytest under {basepython} (PyPI only)
 setenv =
     COV_CORE_SOURCE =
     PYTEST_ADDOPTS = --color=yes --cov=xscen --strict-markers --verbose
     PYTHONPATH = {toxinidir}
 passenv =
     COVERALLS_*
-    ESMFMKFILE
-    ESMF_VERSION
     GITHUB_*
 download = true
 deps =
     coveralls: coveralls
-    esmpy: git+https://github.com/esmf-org/esmf.git@v{env:ESMF_VERSION}\#subdirectory=src/addon/esmpy
 extras =
     dev
-conda_channels =
-    conda-forge
-    defaults
-conda_deps =
-    pytest
-    pytest-cov
-    xdoctest
-conda_env = environment.yml
 install_command = python -m pip install --no-user {opts} {packages}
 commands_pre =
     pip list

xscen/aggregate.py

@@ -18,7 +18,11 @@
 import xarray as xr
 import xclim as xc
 import xclim.core.calendar
-import xesmf as xe
+
+try:
+    import xesmf as xe
+except ImportError:
+    xe = None
 from xclim.core.indicator import Indicator
 
 from .config import parse_config
@@ -930,6 +934,11 @@ def spatial_mean(  # noqa: C901
 
     # Uses xesmf.SpatialAverager
     elif method == "xesmf":
+        if xe is None:
+            raise ImportError(
+                "Method xesmf requires xESMF to work, please install that package."
+            )
+
         # If the region is a bounding box, call shapely and geopandas to transform it into an input compatible with xesmf
         if region["method"] == "bbox":
             polygon_geom = shapely.box(

xscen/regrid.py

@@ -11,7 +11,13 @@
 import cf_xarray as cfxr
 import numpy as np
 import xarray as xr
-import xesmf as xe
+
+try:
+    import xesmf as xe
+    from xesmf.frontend import Regridder
+except ImportError:
+    xe = None
+    Regridder = "xesmf.Regridder"
 
 from .config import parse_config
 
@@ -75,6 +81,11 @@ def regrid_dataset(  # noqa: C901
     --------
     xesmf.regridder, xesmf.util.cf_grid_2d
     """
+    if xe is None:
+        raise ImportError(
+            "xscen's regridding functionality requires xESMF to work, please install that package."
+        )
+
     regridder_kwargs = regridder_kwargs or {}
 
     ds_grids = []  # list of target grids
@@ -293,7 +304,7 @@ def _regridder(
     method: str = "bilinear",
     unmapped_to_nan: Optional[bool] = True,
     **kwargs,
-) -> xe.frontend.Regridder:
+) -> Regridder:
     """Call to xesmf Regridder with a few default arguments.
 
     Parameters