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Possible Regression: 'Float32' object has no attribute 'value' raised when using zarr>3.0.10. #3396

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Closed
Possible Regression: 'Float32' object has no attribute 'value' raised when using zarr>3.0.10.#3396
Labels
bugPotential issues with the zarr-python library

Description

@jbusecke
jbusecke
opened on Aug 21, 2025

Zarr version

main@94983362f06f9bb4be3f04562b179549e36a87c4

Numcodecs version

0.16.2

Python Version

3.12.9

Operating System

Mac

Installation

uv

Description

I was trying to test #3369 for a project using titiler-multidim together with @maxrjones earlier, and ran into this issue.

I wrote out a native zarr v3 dataset (I believe it was using v3.0.8) on the NASA veda hub and downloaded it locally for testing. When I am trying to read that in with the newest version or the main branch I get the following error:

Traceback (most recent call last):
File "/Users/juliusbusecke/Code/titiler-multidim/temp_dont_commit/mre_object_has_no_attr_value.py", line 19, in <module>
ds = xr.open_dataset(
^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/api.py", line 679, in open_dataset
backend_ds = backend.open_dataset(
^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 1581, in open_dataset
ds = store_entrypoint.open_dataset(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/store.py", line 44, in open_dataset
vars, attrs = filename_or_obj.load()
^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/common.py", line 312, in load
(_decode_variable_name(k), v) for k, v in self.get_variables().items()
^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 858, in get_variables
return FrozenDict((k, self.open_store_variable(k)) for k in self.array_keys())
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/core/utils.py", line 415, in FrozenDict
return Frozen(dict(*args, **kwargs))
^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 858, in <genexpr>
return FrozenDict((k, self.open_store_variable(k)) for k in self.array_keys())
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 852, in open_store_variable
attributes["_FillValue"], original_zarr_dtype.value
^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Float32' object has no attribute 'value'

If I downgrade to v3.0.10 the read works fine, so I am wondering if this is a regression. I am a bit confused because Max showed me the regression tests which should cover exactly this case.

I uploaded the dataset to a public bucket, so the script below should be fully repoducible and the dataset inspectable. Thankfull for any pointers.

Steps to reproduce

# /// script# requires-python = ">=3.10"# dependencies = [# "fsspec==2024.12.0",# "s3fs==2024.12.0",# "xarray==2025.1.1",# "zarr @ git+https://github.com/zarr-developers/zarr-python@94983362f06f9bb4be3f04562b179549e36a87c4"# ]# ///# To reproduce failure use dependencies above. To fix, swap "zarr @ git+https://github.com/zarr-developers/zarr-python@94983362f06f9bb4be3f04562b179549e36a87c4" for "zarr==3.0.10"importxarrayasxrimportzarrzarr.print_debug_info()
ds=xr.open_dataset(
"s3://s3://nasa-eodc-public/jbusecke/reproducers/nldas3_subsampled.zarr",
engine='zarr',
storage_options={
"anon": True
}
)
print(ds)

Additional output

Required dependencies:
packaging: 25.0
numpy: 2.3.2
numcodecs: 0.16.2
typing_extensions: 4.14.1
donfig: 0.8.1.post1

Optional dependencies:
botocore: 1.39.11
fsspec: 2024.12.0
numcodecs: 0.16.2
s3fs: 2024.12.0

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Possible Regression: `'Float32' object has no attribute 'value'` raised when using zarr>3.0.10. · Issue #3396 · zarr-developers/zarr-python · GitHub
      Skip to content
      Possible Regression: 'Float32' object has no attribute 'value' raised when using zarr>3.0.10. #3396
      Closed
      Closed
      Possible Regression: 'Float32' object has no attribute 'value' raised when using zarr>3.0.10.#3396
      Labels
      bugPotential issues with the zarr-python library
      Description
      @jbusecke
      jbusecke
      opened on Aug 21, 2025
      Zarr version
      main@94983362f06f9bb4be3f04562b179549e36a87c4
      Numcodecs version
      0.16.2
      Python Version
      3.12.9
      Operating System
      Mac
      Installation
      uv
      Description
      I was trying to test #3369 for a project using titiler-multidim together with @maxrjones earlier, and ran into this issue.
      I wrote out a native zarr v3 dataset (I believe it was using v3.0.8) on the NASA veda hub and downloaded it locally for testing. When I am trying to read that in with the newest version or the main branch I get the following error:
      Traceback (most recent call last):
File "/Users/juliusbusecke/Code/titiler-multidim/temp_dont_commit/mre_object_has_no_attr_value.py", line 19, in <module>
ds = xr.open_dataset(
^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/api.py", line 679, in open_dataset
backend_ds = backend.open_dataset(
^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 1581, in open_dataset
ds = store_entrypoint.open_dataset(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/store.py", line 44, in open_dataset
vars, attrs = filename_or_obj.load()
^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/common.py", line 312, in load
(_decode_variable_name(k), v) for k, v in self.get_variables().items()
^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 858, in get_variables
return FrozenDict((k, self.open_store_variable(k)) for k in self.array_keys())
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/core/utils.py", line 415, in FrozenDict
return Frozen(dict(*args, **kwargs))
^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 858, in <genexpr>
return FrozenDict((k, self.open_store_variable(k)) for k in self.array_keys())
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 852, in open_store_variable
attributes["_FillValue"], original_zarr_dtype.value
^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Float32' object has no attribute 'value'

      If I downgrade to v3.0.10 the read works fine, so I am wondering if this is a regression. I am a bit confused because Max showed me the regression tests which should cover exactly this case.
      I uploaded the dataset to a public bucket, so the script below should be fully repoducible and the dataset inspectable. Thankfull for any pointers.
      Steps to reproduce
      # /// script# requires-python = ">=3.10"# dependencies = [# "fsspec==2024.12.0",# "s3fs==2024.12.0",# "xarray==2025.1.1",# "zarr @ git+https://github.com/zarr-developers/zarr-python@94983362f06f9bb4be3f04562b179549e36a87c4"# ]# ///# To reproduce failure use dependencies above. To fix, swap "zarr @ git+https://github.com/zarr-developers/zarr-python@94983362f06f9bb4be3f04562b179549e36a87c4" for "zarr==3.0.10"importxarrayasxrimportzarrzarr.print_debug_info()
ds=xr.open_dataset(
"s3://s3://nasa-eodc-public/jbusecke/reproducers/nldas3_subsampled.zarr",
engine='zarr',
storage_options={
"anon": True
}
)
print(ds)
      Additional output
      Required dependencies:
      
packaging: 25.0
      
numpy: 2.3.2
      
numcodecs: 0.16.2
      
typing_extensions: 4.14.1
      
donfig: 0.8.1.post1
      Optional dependencies:
      
botocore: 1.39.11
      
fsspec: 2024.12.0
      
numcodecs: 0.16.2
      
s3fs: 2024.12.0
      Metadata
      Metadata
      Assignees
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        Labels
        bugPotential issues with the zarr-python library
        Type
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        No projects
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, 'i');
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var __m = "*";
var __re = new RegExp('^' + ".*" + '
Possible Regression: `'Float32' object has no attribute 'value'` raised when using zarr>3.0.10. · Issue #3396 · zarr-developers/zarr-python · GitHub
          Skip to content
          Possible Regression: 'Float32' object has no attribute 'value' raised when using zarr>3.0.10. #3396
          Closed
          Closed
          Possible Regression: 'Float32' object has no attribute 'value' raised when using zarr>3.0.10.#3396
          Labels
          bugPotential issues with the zarr-python library
          Description
          @jbusecke
          jbusecke
          opened on Aug 21, 2025
          Zarr version
          main@94983362f06f9bb4be3f04562b179549e36a87c4
          Numcodecs version
          0.16.2
          Python Version
          3.12.9
          Operating System
          Mac
          Installation
          uv
          Description
          I was trying to test #3369 for a project using titiler-multidim together with @maxrjones earlier, and ran into this issue.
          I wrote out a native zarr v3 dataset (I believe it was using v3.0.8) on the NASA veda hub and downloaded it locally for testing. When I am trying to read that in with the newest version or the main branch I get the following error:
          Traceback (most recent call last):
File "/Users/juliusbusecke/Code/titiler-multidim/temp_dont_commit/mre_object_has_no_attr_value.py", line 19, in <module>
ds = xr.open_dataset(
^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/api.py", line 679, in open_dataset
backend_ds = backend.open_dataset(
^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 1581, in open_dataset
ds = store_entrypoint.open_dataset(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/store.py", line 44, in open_dataset
vars, attrs = filename_or_obj.load()
^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/common.py", line 312, in load
(_decode_variable_name(k), v) for k, v in self.get_variables().items()
^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 858, in get_variables
return FrozenDict((k, self.open_store_variable(k)) for k in self.array_keys())
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/core/utils.py", line 415, in FrozenDict
return Frozen(dict(*args, **kwargs))
^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 858, in <genexpr>
return FrozenDict((k, self.open_store_variable(k)) for k in self.array_keys())
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 852, in open_store_variable
attributes["_FillValue"], original_zarr_dtype.value
^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Float32' object has no attribute 'value'

          If I downgrade to v3.0.10 the read works fine, so I am wondering if this is a regression. I am a bit confused because Max showed me the regression tests which should cover exactly this case.
          I uploaded the dataset to a public bucket, so the script below should be fully repoducible and the dataset inspectable. Thankfull for any pointers.
          Steps to reproduce
          # /// script# requires-python = ">=3.10"# dependencies = [# "fsspec==2024.12.0",# "s3fs==2024.12.0",# "xarray==2025.1.1",# "zarr @ git+https://github.com/zarr-developers/zarr-python@94983362f06f9bb4be3f04562b179549e36a87c4"# ]# ///# To reproduce failure use dependencies above. To fix, swap "zarr @ git+https://github.com/zarr-developers/zarr-python@94983362f06f9bb4be3f04562b179549e36a87c4" for "zarr==3.0.10"importxarrayasxrimportzarrzarr.print_debug_info()
ds=xr.open_dataset(
"s3://s3://nasa-eodc-public/jbusecke/reproducers/nldas3_subsampled.zarr",
engine='zarr',
storage_options={
"anon": True
}
)
print(ds)
          Additional output
          Required dependencies:
          
packaging: 25.0
          
numpy: 2.3.2
          
numcodecs: 0.16.2
          
typing_extensions: 4.14.1
          
donfig: 0.8.1.post1
          Optional dependencies:
          
botocore: 1.39.11
          
fsspec: 2024.12.0
          
numcodecs: 0.16.2
          
s3fs: 2024.12.0
          Metadata
          Metadata
          Assignees
          No one assigned
            Labels
            bugPotential issues with the zarr-python library
            Type
            No type
            Projects
            No projects
              Milestone
              No milestone
              Relationships
              None yet
              Development
              No branches or pull requests
              Issue actions
              
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var __m = "*";
var __re = new RegExp('^' + ".*" + '
Possible Regression: `'Float32' object has no attribute 'value'` raised when using zarr>3.0.10. · Issue #3396 · zarr-developers/zarr-python · GitHub
              Skip to content
              Possible Regression: 'Float32' object has no attribute 'value' raised when using zarr>3.0.10. #3396
              Closed
              Closed
              Possible Regression: 'Float32' object has no attribute 'value' raised when using zarr>3.0.10.#3396
              Labels
              bugPotential issues with the zarr-python library
              Description
              @jbusecke
              jbusecke
              opened on Aug 21, 2025
              Zarr version
              main@94983362f06f9bb4be3f04562b179549e36a87c4
              Numcodecs version
              0.16.2
              Python Version
              3.12.9
              Operating System
              Mac
              Installation
              uv
              Description
              I was trying to test #3369 for a project using titiler-multidim together with @maxrjones earlier, and ran into this issue.
              I wrote out a native zarr v3 dataset (I believe it was using v3.0.8) on the NASA veda hub and downloaded it locally for testing. When I am trying to read that in with the newest version or the main branch I get the following error:
              Traceback (most recent call last):
File "/Users/juliusbusecke/Code/titiler-multidim/temp_dont_commit/mre_object_has_no_attr_value.py", line 19, in <module>
ds = xr.open_dataset(
^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/api.py", line 679, in open_dataset
backend_ds = backend.open_dataset(
^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 1581, in open_dataset
ds = store_entrypoint.open_dataset(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/store.py", line 44, in open_dataset
vars, attrs = filename_or_obj.load()
^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/common.py", line 312, in load
(_decode_variable_name(k), v) for k, v in self.get_variables().items()
^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 858, in get_variables
return FrozenDict((k, self.open_store_variable(k)) for k in self.array_keys())
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/core/utils.py", line 415, in FrozenDict
return Frozen(dict(*args, **kwargs))
^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 858, in <genexpr>
return FrozenDict((k, self.open_store_variable(k)) for k in self.array_keys())
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 852, in open_store_variable
attributes["_FillValue"], original_zarr_dtype.value
^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Float32' object has no attribute 'value'

              If I downgrade to v3.0.10 the read works fine, so I am wondering if this is a regression. I am a bit confused because Max showed me the regression tests which should cover exactly this case.
              I uploaded the dataset to a public bucket, so the script below should be fully repoducible and the dataset inspectable. Thankfull for any pointers.
              Steps to reproduce
              # /// script# requires-python = ">=3.10"# dependencies = [# "fsspec==2024.12.0",# "s3fs==2024.12.0",# "xarray==2025.1.1",# "zarr @ git+https://github.com/zarr-developers/zarr-python@94983362f06f9bb4be3f04562b179549e36a87c4"# ]# ///# To reproduce failure use dependencies above. To fix, swap "zarr @ git+https://github.com/zarr-developers/zarr-python@94983362f06f9bb4be3f04562b179549e36a87c4" for "zarr==3.0.10"importxarrayasxrimportzarrzarr.print_debug_info()
ds=xr.open_dataset(
"s3://s3://nasa-eodc-public/jbusecke/reproducers/nldas3_subsampled.zarr",
engine='zarr',
storage_options={
"anon": True
}
)
print(ds)
              Additional output
              Required dependencies:
              
packaging: 25.0
              
numpy: 2.3.2
              
numcodecs: 0.16.2
              
typing_extensions: 4.14.1
              
donfig: 0.8.1.post1
              Optional dependencies:
              
botocore: 1.39.11
              
fsspec: 2024.12.0
              
numcodecs: 0.16.2
              
s3fs: 2024.12.0
              Metadata
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                  Issue actions
                  
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Possible Regression: `'Float32' object has no attribute 'value'` raised when using zarr>3.0.10. · Issue #3396 · zarr-developers/zarr-python · GitHub
                  Skip to content
                  Possible Regression: 'Float32' object has no attribute 'value' raised when using zarr>3.0.10. #3396
                  Closed
                  Closed
                  Possible Regression: 'Float32' object has no attribute 'value' raised when using zarr>3.0.10.#3396
                  Labels
                  bugPotential issues with the zarr-python library
                  Description
                  @jbusecke
                  jbusecke
                  opened on Aug 21, 2025
                  Zarr version
                  main@94983362f06f9bb4be3f04562b179549e36a87c4
                  Numcodecs version
                  0.16.2
                  Python Version
                  3.12.9
                  Operating System
                  Mac
                  Installation
                  uv
                  Description
                  I was trying to test #3369 for a project using titiler-multidim together with @maxrjones earlier, and ran into this issue.
                  I wrote out a native zarr v3 dataset (I believe it was using v3.0.8) on the NASA veda hub and downloaded it locally for testing. When I am trying to read that in with the newest version or the main branch I get the following error:
                  Traceback (most recent call last):
File "/Users/juliusbusecke/Code/titiler-multidim/temp_dont_commit/mre_object_has_no_attr_value.py", line 19, in <module>
ds = xr.open_dataset(
^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/api.py", line 679, in open_dataset
backend_ds = backend.open_dataset(
^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 1581, in open_dataset
ds = store_entrypoint.open_dataset(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/store.py", line 44, in open_dataset
vars, attrs = filename_or_obj.load()
^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/common.py", line 312, in load
(_decode_variable_name(k), v) for k, v in self.get_variables().items()
^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 858, in get_variables
return FrozenDict((k, self.open_store_variable(k)) for k in self.array_keys())
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/core/utils.py", line 415, in FrozenDict
return Frozen(dict(*args, **kwargs))
^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 858, in <genexpr>
return FrozenDict((k, self.open_store_variable(k)) for k in self.array_keys())
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 852, in open_store_variable
attributes["_FillValue"], original_zarr_dtype.value
^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Float32' object has no attribute 'value'

                  If I downgrade to v3.0.10 the read works fine, so I am wondering if this is a regression. I am a bit confused because Max showed me the regression tests which should cover exactly this case.
                  I uploaded the dataset to a public bucket, so the script below should be fully repoducible and the dataset inspectable. Thankfull for any pointers.
                  Steps to reproduce
                  # /// script# requires-python = ">=3.10"# dependencies = [# "fsspec==2024.12.0",# "s3fs==2024.12.0",# "xarray==2025.1.1",# "zarr @ git+https://github.com/zarr-developers/zarr-python@94983362f06f9bb4be3f04562b179549e36a87c4"# ]# ///# To reproduce failure use dependencies above. To fix, swap "zarr @ git+https://github.com/zarr-developers/zarr-python@94983362f06f9bb4be3f04562b179549e36a87c4" for "zarr==3.0.10"importxarrayasxrimportzarrzarr.print_debug_info()
ds=xr.open_dataset(
"s3://s3://nasa-eodc-public/jbusecke/reproducers/nldas3_subsampled.zarr",
engine='zarr',
storage_options={
"anon": True
}
)
print(ds)
                  Additional output
                  Required dependencies:
                  
packaging: 25.0
                  
numpy: 2.3.2
                  
numcodecs: 0.16.2
                  
typing_extensions: 4.14.1
                  
donfig: 0.8.1.post1
                  Optional dependencies:
                  
botocore: 1.39.11
                  
fsspec: 2024.12.0
                  
numcodecs: 0.16.2
                  
s3fs: 2024.12.0
                  Metadata
                  Metadata
                  Assignees
                  No one assigned
                    Labels
                    bugPotential issues with the zarr-python library
                    Type
                    No type
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                    No projects
                      Milestone
                      No milestone
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                      None yet
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                      No branches or pull requests
                      Issue actions
                      
, 'i');
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var __m = "*";
var __re = new RegExp('^' + ".*" + '
Possible Regression: `'Float32' object has no attribute 'value'` raised when using zarr>3.0.10. · Issue #3396 · zarr-developers/zarr-python · GitHub
                      Skip to content
                      Possible Regression: 'Float32' object has no attribute 'value' raised when using zarr>3.0.10. #3396
                      Closed
                      Closed
                      Possible Regression: 'Float32' object has no attribute 'value' raised when using zarr>3.0.10.#3396
                      Labels
                      bugPotential issues with the zarr-python library
                      Description
                      @jbusecke
                      jbusecke
                      opened on Aug 21, 2025
                      Zarr version
                      main@94983362f06f9bb4be3f04562b179549e36a87c4
                      Numcodecs version
                      0.16.2
                      Python Version
                      3.12.9
                      Operating System
                      Mac
                      Installation
                      uv
                      Description
                      I was trying to test #3369 for a project using titiler-multidim together with @maxrjones earlier, and ran into this issue.
                      I wrote out a native zarr v3 dataset (I believe it was using v3.0.8) on the NASA veda hub and downloaded it locally for testing. When I am trying to read that in with the newest version or the main branch I get the following error:
                      Traceback (most recent call last):
File "/Users/juliusbusecke/Code/titiler-multidim/temp_dont_commit/mre_object_has_no_attr_value.py", line 19, in <module>
ds = xr.open_dataset(
^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/api.py", line 679, in open_dataset
backend_ds = backend.open_dataset(
^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 1581, in open_dataset
ds = store_entrypoint.open_dataset(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/store.py", line 44, in open_dataset
vars, attrs = filename_or_obj.load()
^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/common.py", line 312, in load
(_decode_variable_name(k), v) for k, v in self.get_variables().items()
^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 858, in get_variables
return FrozenDict((k, self.open_store_variable(k)) for k in self.array_keys())
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/core/utils.py", line 415, in FrozenDict
return Frozen(dict(*args, **kwargs))
^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 858, in <genexpr>
return FrozenDict((k, self.open_store_variable(k)) for k in self.array_keys())
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 852, in open_store_variable
attributes["_FillValue"], original_zarr_dtype.value
^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Float32' object has no attribute 'value'

                      If I downgrade to v3.0.10 the read works fine, so I am wondering if this is a regression. I am a bit confused because Max showed me the regression tests which should cover exactly this case.
                      I uploaded the dataset to a public bucket, so the script below should be fully repoducible and the dataset inspectable. Thankfull for any pointers.
                      Steps to reproduce
                      # /// script# requires-python = ">=3.10"# dependencies = [# "fsspec==2024.12.0",# "s3fs==2024.12.0",# "xarray==2025.1.1",# "zarr @ git+https://github.com/zarr-developers/zarr-python@94983362f06f9bb4be3f04562b179549e36a87c4"# ]# ///# To reproduce failure use dependencies above. To fix, swap "zarr @ git+https://github.com/zarr-developers/zarr-python@94983362f06f9bb4be3f04562b179549e36a87c4" for "zarr==3.0.10"importxarrayasxrimportzarrzarr.print_debug_info()
ds=xr.open_dataset(
"s3://s3://nasa-eodc-public/jbusecke/reproducers/nldas3_subsampled.zarr",
engine='zarr',
storage_options={
"anon": True
}
)
print(ds)
                      Additional output
                      Required dependencies:
                      
packaging: 25.0
                      
numpy: 2.3.2
                      
numcodecs: 0.16.2
                      
typing_extensions: 4.14.1
                      
donfig: 0.8.1.post1
                      Optional dependencies:
                      
botocore: 1.39.11
                      
fsspec: 2024.12.0
                      
numcodecs: 0.16.2
                      
s3fs: 2024.12.0
                      Metadata
                      Metadata
                      Assignees
                      No one assigned
                        Labels
                        bugPotential issues with the zarr-python library
                        Type
                        No type
                        Projects
                        No projects
                          Milestone
                          No milestone
                          Relationships
                          None yet
                          Development
                          No branches or pull requests
                          Issue actions
                          
, 'i');
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(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Possible Regression: `'Float32' object has no attribute 'value'` raised when using zarr>3.0.10. · Issue #3396 · zarr-developers/zarr-python · GitHub
                          Skip to content
                          Possible Regression: 'Float32' object has no attribute 'value' raised when using zarr>3.0.10. #3396
                          Closed
                          Closed
                          Possible Regression: 'Float32' object has no attribute 'value' raised when using zarr>3.0.10.#3396
                          Labels
                          bugPotential issues with the zarr-python library
                          Description
                          @jbusecke
                          jbusecke
                          opened on Aug 21, 2025
                          Zarr version
                          main@94983362f06f9bb4be3f04562b179549e36a87c4
                          Numcodecs version
                          0.16.2
                          Python Version
                          3.12.9
                          Operating System
                          Mac
                          Installation
                          uv
                          Description
                          I was trying to test #3369 for a project using titiler-multidim together with @maxrjones earlier, and ran into this issue.
                          I wrote out a native zarr v3 dataset (I believe it was using v3.0.8) on the NASA veda hub and downloaded it locally for testing. When I am trying to read that in with the newest version or the main branch I get the following error:
                          Traceback (most recent call last):
File "/Users/juliusbusecke/Code/titiler-multidim/temp_dont_commit/mre_object_has_no_attr_value.py", line 19, in <module>
ds = xr.open_dataset(
^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/api.py", line 679, in open_dataset
backend_ds = backend.open_dataset(
^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 1581, in open_dataset
ds = store_entrypoint.open_dataset(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/store.py", line 44, in open_dataset
vars, attrs = filename_or_obj.load()
^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/common.py", line 312, in load
(_decode_variable_name(k), v) for k, v in self.get_variables().items()
^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 858, in get_variables
return FrozenDict((k, self.open_store_variable(k)) for k in self.array_keys())
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/core/utils.py", line 415, in FrozenDict
return Frozen(dict(*args, **kwargs))
^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 858, in <genexpr>
return FrozenDict((k, self.open_store_variable(k)) for k in self.array_keys())
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 852, in open_store_variable
attributes["_FillValue"], original_zarr_dtype.value
^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Float32' object has no attribute 'value'

                          If I downgrade to v3.0.10 the read works fine, so I am wondering if this is a regression. I am a bit confused because Max showed me the regression tests which should cover exactly this case.
                          I uploaded the dataset to a public bucket, so the script below should be fully repoducible and the dataset inspectable. Thankfull for any pointers.
                          Steps to reproduce
                          # /// script# requires-python = ">=3.10"# dependencies = [# "fsspec==2024.12.0",# "s3fs==2024.12.0",# "xarray==2025.1.1",# "zarr @ git+https://github.com/zarr-developers/zarr-python@94983362f06f9bb4be3f04562b179549e36a87c4"# ]# ///# To reproduce failure use dependencies above. To fix, swap "zarr @ git+https://github.com/zarr-developers/zarr-python@94983362f06f9bb4be3f04562b179549e36a87c4" for "zarr==3.0.10"importxarrayasxrimportzarrzarr.print_debug_info()
ds=xr.open_dataset(
"s3://s3://nasa-eodc-public/jbusecke/reproducers/nldas3_subsampled.zarr",
engine='zarr',
storage_options={
"anon": True
}
)
print(ds)
                          Additional output
                          Required dependencies:
                          
packaging: 25.0
                          
numpy: 2.3.2
                          
numcodecs: 0.16.2
                          
typing_extensions: 4.14.1
                          
donfig: 0.8.1.post1
                          Optional dependencies:
                          
botocore: 1.39.11
                          
fsspec: 2024.12.0
                          
numcodecs: 0.16.2
                          
s3fs: 2024.12.0
                          Metadata
                          Metadata
                          Assignees
                          No one assigned
                            Labels
                            bugPotential issues with the zarr-python library
                            Type
                            No type
                            Projects
                            No projects
                              Milestone
                              No milestone
                              Relationships
                              None yet
                              Development
                              No branches or pull requests
                              Issue actions
                              
, 'i');
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Possible Regression: `'Float32' object has no attribute 'value'` raised when using zarr>3.0.10. · Issue #3396 · zarr-developers/zarr-python · GitHub
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                              Possible Regression: 'Float32' object has no attribute 'value' raised when using zarr>3.0.10. #3396
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                              Closed
                              Possible Regression: 'Float32' object has no attribute 'value' raised when using zarr>3.0.10.#3396
                              Labels
                              bugPotential issues with the zarr-python library
                              Description
                              @jbusecke
                              jbusecke
                              opened on Aug 21, 2025
                              Zarr version
                              main@94983362f06f9bb4be3f04562b179549e36a87c4
                              Numcodecs version
                              0.16.2
                              Python Version
                              3.12.9
                              Operating System
                              Mac
                              Installation
                              uv
                              Description
                              I was trying to test #3369 for a project using titiler-multidim together with @maxrjones earlier, and ran into this issue.
                              I wrote out a native zarr v3 dataset (I believe it was using v3.0.8) on the NASA veda hub and downloaded it locally for testing. When I am trying to read that in with the newest version or the main branch I get the following error:
                              Traceback (most recent call last):
File "/Users/juliusbusecke/Code/titiler-multidim/temp_dont_commit/mre_object_has_no_attr_value.py", line 19, in <module>
ds = xr.open_dataset(
^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/api.py", line 679, in open_dataset
backend_ds = backend.open_dataset(
^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 1581, in open_dataset
ds = store_entrypoint.open_dataset(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/store.py", line 44, in open_dataset
vars, attrs = filename_or_obj.load()
^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/common.py", line 312, in load
(_decode_variable_name(k), v) for k, v in self.get_variables().items()
^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 858, in get_variables
return FrozenDict((k, self.open_store_variable(k)) for k in self.array_keys())
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/core/utils.py", line 415, in FrozenDict
return Frozen(dict(*args, **kwargs))
^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 858, in <genexpr>
return FrozenDict((k, self.open_store_variable(k)) for k in self.array_keys())
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/juliusbusecke/.cache/uv/environments-v2/mre-object-has-no-attr-value-cd1317b944d0d9b9/lib/python3.12/site-packages/xarray/backends/zarr.py", line 852, in open_store_variable
attributes["_FillValue"], original_zarr_dtype.value
^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Float32' object has no attribute 'value'

                              If I downgrade to v3.0.10 the read works fine, so I am wondering if this is a regression. I am a bit confused because Max showed me the regression tests which should cover exactly this case.
                              I uploaded the dataset to a public bucket, so the script below should be fully repoducible and the dataset inspectable. Thankfull for any pointers.
                              Steps to reproduce
                              # /// script# requires-python = ">=3.10"# dependencies = [# "fsspec==2024.12.0",# "s3fs==2024.12.0",# "xarray==2025.1.1",# "zarr @ git+https://github.com/zarr-developers/zarr-python@94983362f06f9bb4be3f04562b179549e36a87c4"# ]# ///# To reproduce failure use dependencies above. To fix, swap "zarr @ git+https://github.com/zarr-developers/zarr-python@94983362f06f9bb4be3f04562b179549e36a87c4" for "zarr==3.0.10"importxarrayasxrimportzarrzarr.print_debug_info()
ds=xr.open_dataset(
"s3://s3://nasa-eodc-public/jbusecke/reproducers/nldas3_subsampled.zarr",
engine='zarr',
storage_options={
"anon": True
}
)
print(ds)
                              Additional output
                              Required dependencies:
                              
packaging: 25.0
                              
numpy: 2.3.2
                              
numcodecs: 0.16.2
                              
typing_extensions: 4.14.1
                              
donfig: 0.8.1.post1
                              Optional dependencies:
                              
botocore: 1.39.11
                              
fsspec: 2024.12.0
                              
numcodecs: 0.16.2
                              
s3fs: 2024.12.0
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