Nearest / KDTree resampling fails if `numcodecs>=0.16`

[needham-michael]

Describe the bug
Calling scene.resample(...) fails with KeyError: "Resampler 'kd_tree' not available" when user's numcodecs>=0.16, which seems to be related to zarr-developers/numcodecs#721. The example below resamples as expected when run with numcodecs=0.15.1 but fails when run with numcodecs=0.16.5.

I dug into this a bit and it appears that the problem stems from _get_resampler_classes_from_module within satpy.resample.base..py. It seems that the with suppress(ImportError) statement within _get_resampler_classes_from_module suppresses the ImportError which would have been raised from import zarr within satpy.resample.kdtree.py. In that case _get_resampler_classes_from_module returns no resampler classes from satpy.resample.kdtree.py, which then gives the user the error listed above.

To Reproduce

# Script downloads a VIIRS L2 cloud mask granule from NASA earthacces 
# as an example to demonstrate the resample error behavior. But can likely 
# reproduce with a different file supplied to granule_files
import earthaccess
import numcodecs
from pyresample import create_area_def
from satpy.scene import Scene

earthaccess.login()

bounding_box = (-97.75, 35.75, -95.25, 39.75)
granule_files = None

if granule_files is None:
    
    local_path = ./'

    granule_search_results_cldmask = earthaccess.search_data(
        short_name="CLDMSK_L2_VIIRS_SNPP",
        bounding_box=bounding_box,
        temporal=('2025-04-06', '2025-04-06'),
        day_night_flag='day',
        instrument='VIIRS',
        platform='SUOMI-NPP'  
    )
    
    granule_files = earthaccess.download(
        granule_search_results_cldmask,
        local_path = local_path
    )

area_def = create_area_def(
    "area_name",
    {'proj': 'lcc', 'lon_0': -95, 'lat_0': 25, 'lat_1': 35},
    width=500,
    height=1000,
    area_extent=bounding_box,
    units='degrees'
)

print(f"{numcodecs.__version__ = }")

scene = Scene(granule_files,reader='viirs_l2')
scene.load(scene.available_dataset_names())
scene_resampled = scene.resample(area_def) # <- Fails here if numcodecs>=0.16
scene_resampled.load(scene.available_dataset_names())

  

Environment Info:

• OS: Windows 11 Enterprise
• Satpy Version: 0.59.0
• PyResample Version: 1.35.0

Output from uv pip list:

Package                   Version     Editable project location
------------------------- ----------- --------------------------------------------------------------------------------------------------
affine                    2.4.0
aggdraw                   1.4.1
aiobotocore               3.1.3
aiohappyeyeballs          2.6.1
aiohttp                   3.13.3
aioitertools              0.13.0
aiosignal                 1.4.0
anyio                     4.12.1
argon2-cffi               25.1.0
argon2-cffi-bindings      25.1.0
arrow                     1.4.0
asciitree                 0.3.3
asttokens                 3.0.1
async-lru                 2.1.0
attrs                     25.4.0
babel                     2.18.0
beautifulsoup4            4.14.3
bleach                    6.3.0
bokeh                     3.8.2
botocore                  1.42.49
bottleneck                1.6.0
bounded-pool-executor     0.0.3
cartopy                   0.25.0
certifi                   2026.1.4
cffi                      2.0.0
cftime                    1.6.5
charset-normalizer        3.4.4
click                     8.3.1
cligj                     0.7.2
cloudpickle               3.1.2
colorama                  0.4.6
colorcet                  3.1.0
comm                      0.2.3
configobj                 5.0.9
contourpy                 1.3.3
cycler                    0.12.1
dask                      2026.1.2
debugpy                   1.8.20
decorator                 5.2.1
defusedxml                0.7.1
deprecated                1.3.1
donfig                    0.8.1.post1
earthaccess               0.16.0
executing                 2.2.1
fasteners                 0.20
fastjsonschema            2.21.2
fonttools                 4.61.1
fqdn                      1.5.1
frozenlist                1.8.0
fsspec                    2026.2.0
geopandas                 1.1.2
geotiff                   0.2.10
geoviews                  1.15.1
h11                       0.16.0
h5netcdf                  1.8.1
h5py                      3.15.1
holoviews                 1.22.1
httpcore                  1.0.9
httpx                     0.28.1
hvplot                    0.12.2
idna                      3.11
importlib-resources       6.5.2
ipykernel                 7.2.0
ipython                   9.10.0
ipython-pygments-lexers   1.1.1
ipywidgets                8.1.8
isoduration               20.11.0
jedi                      0.19.2
jinja2                    3.1.6
jmespath                  1.1.0
joblib                    1.5.3
json5                     0.13.0
jsonpointer               3.0.0
jsonschema                4.26.0
jsonschema-specifications 2025.9.1
jupyter-client            8.8.0
jupyter-core              5.9.1
jupyter-events            0.12.0
jupyter-lsp               2.3.0
jupyter-server            2.17.0
jupyter-server-terminals  0.5.4
jupyterlab                4.5.4
jupyterlab-pygments       0.3.0
jupyterlab-server         2.28.0
jupyterlab-widgets        3.0.16
kiwisolver                1.4.9
lark                      1.3.1
linkify-it-py             2.0.3
locket                    1.0.0
markdown                  3.10.2
markdown-it-py            4.0.0
markupsafe                3.0.3
matplotlib                3.10.8
matplotlib-inline         0.2.1
mdit-py-plugins           0.5.0
mdurl                     0.1.2
mistune                   3.2.0
multidict                 6.7.1
multimethod               2.0.2
narwhals                  2.16.0
nbclient                  0.10.4
nbconvert                 7.17.0
nbformat                  5.10.4
nest-asyncio              1.6.0
netcdf4                   1.7.4
notebook-shim             0.2.4
numcodecs                 0.16.5
numpy                     2.4.2
packaging                 26.0
pandas                    3.0.1
pandocfilters             1.5.1
panel                     1.8.7
param                     2.3.2
parso                     0.8.6
partd                     1.4.2
pathlib-abc               0.5.2
pillow                    12.1.1
platformdirs              4.9.2
pooch                     1.9.0
pqdm                      0.2.0
prometheus-client         0.24.1
prompt-toolkit            3.0.52
propcache                 0.4.1
psutil                    7.2.2
pure-eval                 0.2.3
pyarrow                   23.0.1
pycoast                   1.8.0
pycparser                 3.0
pydecorate                0.5.0
pygments                  2.19.2
pykdtree                  1.4.3
pyogrio                   0.12.1
pyorbital                 1.12.0
pyparsing                 3.3.2
pyproj                    3.7.2
pyresample                1.35.0
pyshp                     3.0.3
pyspectral                0.14.1
python-cmr                0.13.0
python-dateutil           2.9.0.post0
python-geotiepoints       1.9.0
python-json-logger        4.0.0
pyviz-comms               3.0.6
pywinpty                  3.0.3
pyyaml                    6.0.3
pyzmq                     27.1.0
rasterio                  1.5.0
referencing               0.37.0
requests                  2.32.5
rfc3339-validator         0.1.4
rfc3986-validator         0.1.1
rfc3987-syntax            1.1.0
rioxarray                 0.21.0
rpds-py                   0.30.0
ruff                      0.15.1
s3fs                      2026.2.0
satpy                     0.59.0
scikit-learn              1.8.0
scipy                     1.17.0
send2trash                2.1.0
setuptools                82.0.0
shapely                   2.1.2
six                       1.17.0
soupsieve                 2.8.3
stack-data                0.6.3
tenacity                  9.1.4
terminado                 0.18.1
threadpoolctl             3.6.0
tifffile                  2026.2.16
tinycss2                  1.4.0
tinynetrc                 1.3.1
toolz                     1.1.0
tornado                   6.5.4
tqdm                      4.67.3
traitlets                 5.14.3
trollimage                1.28.0
trollsift                 1.0.0
typing-extensions         4.15.0
tzdata                    2025.3
uc-micro-py               1.0.3
universal-pathlib         0.3.9
uri-template              1.3.0
urllib3                   2.6.3
wcwidth                   0.6.0
webcolors                 25.10.0
webencodings              0.5.1
websocket-client          1.9.0
widgetsnbextension        4.0.15
wrapt                     2.1.1
xarray                    2025.11.0
xyzservices               2025.11.0
yarl                      1.22.0
zarr                      2.12.0

[djhoese]

Thanks for filing the issue. This is very interesting. @pnuu I think you last refactored/rewrote this code:

satpy/satpy/resample/base.py

Lines 84 to 88 in f5bd750

	def _get_resampler_classes_from_module(import_path):
	with suppress(ImportError):
	mod = import_module(import_path)
	return mod.get_resampler_classes()
	return {}

It seems like the options which could each be done separately:

1. Check if no resamplers are available and log an error or raise an error. However some Satpy use cases may not want/need any resamplers. This is currently first loaded when the first resample call is performed so logging should be setup by that point. The way it is structured does make it hard to map "user's resampler name -> module that failed to import". In the future we want most of this logic to live in pyresample which is similarly difficult to say "I want this resampler, why is it not available".
2. Log each import error for "builtin" resamplers.

One other thing I'm noticing is we probably need some caching on this get_all_resampler_classes call as it recreates this dictionary of resamplers every time resampling is called. Then again, imports are cached by python in sys.modules so it isn't that wasteful.

[pnuu]

Yep, I refactored the multiple try/except blocks with the single with suppress() in #3124 commit 9f9a385 . The numcodecs change would affect also the previous version. Although it would be easier to add the logging Dave mentioned above to the try/except variant.