issues: 2099550299

What happened?

Unstacking fails for array types that strictly follow the array API standard.

What did you expect to happen?

This obviously works fine with a normal numpy array.

Minimal Complete Verifiable Example

```Python import numpy.array_api as nxp

arr = nxp.asarray([[1, 2, 3], [4, 5, 6]], dtype=np.dtype('float32'))

da = xr.DataArray( arr, coords=[("x", ["a", "b"]), ("y", [0, 1, 2])], ) da stacked = da.stack(z=("x", "y")) stacked.indexes["z"] stacked.unstack()

---

AttributeError Traceback (most recent call last) Cell In[65], line 8 6 stacked = da.stack(z=("x", "y")) 7 stacked.indexes["z"] ----> 8 roundtripped = stacked.unstack() 9 arr.identical(roundtripped)

File ~/Documents/Work/Code/xarray/xarray/util/deprecation_helpers.py:115, in _deprecate_positional_args.<locals>._decorator.<locals>.inner(args, kwargs) 111 kwargs.update({name: arg for name, arg in zip_args}) 113 return func(args[:-n_extra_args], kwargs) --> 115 return func(*args, kwargs)

File ~/Documents/Work/Code/xarray/xarray/core/dataarray.py:2913, in DataArray.unstack(self, dim, fill_value, sparse) 2851 @_deprecate_positional_args("v2023.10.0") 2852 def unstack( 2853 self, (...) 2857 sparse: bool = False, 2858 ) -> Self: 2859 """ 2860 Unstack existing dimensions corresponding to MultiIndexes into 2861 multiple new dimensions. (...) 2911 DataArray.stack 2912 """ -> 2913 ds = self._to_temp_dataset().unstack(dim, fill_value=fill_value, sparse=sparse) 2914 return self._from_temp_dataset(ds)

File ~/Documents/Work/Code/xarray/xarray/util/deprecation_helpers.py:115, in _deprecate_positional_args.<locals>._decorator.<locals>.inner(args, kwargs) 111 kwargs.update({name: arg for name, arg in zip_args}) 113 return func(args[:-n_extra_args], kwargs) --> 115 return func(*args, kwargs)

File ~/Documents/Work/Code/xarray/xarray/core/dataset.py:5581, in Dataset.unstack(self, dim, fill_value, sparse) 5579 for d in dims: 5580 if needs_full_reindex: -> 5581 result = result._unstack_full_reindex( 5582 d, stacked_indexes[d], fill_value, sparse 5583 ) 5584 else: 5585 result = result._unstack_once(d, stacked_indexes[d], fill_value, sparse)

File ~/Documents/Work/Code/xarray/xarray/core/dataset.py:5474, in Dataset._unstack_full_reindex(self, dim, index_and_vars, fill_value, sparse) 5472 if name not in index_vars: 5473 if dim in var.dims: -> 5474 variables[name] = var.unstack({dim: new_dim_sizes}) 5475 else: 5476 variables[name] = var

File ~/Documents/Work/Code/xarray/xarray/core/variable.py:1684, in Variable.unstack(self, dimensions, **dimensions_kwargs) 1682 result = self 1683 for old_dim, dims in dimensions.items(): -> 1684 result = result._unstack_once_full(dims, old_dim) 1685 return result

File ~/Documents/Work/Code/xarray/xarray/core/variable.py:1574, in Variable._unstack_once_full(self, dim, old_dim) 1571 reordered = self.transpose(*dim_order) 1573 new_shape = reordered.shape[: len(other_dims)] + new_dim_sizes -> 1574 new_data = reordered.data.reshape(new_shape) 1575 new_dims = reordered.dims[: len(other_dims)] + new_dim_names 1577 return type(self)( 1578 new_dims, new_data, self._attrs, self._encoding, fastpath=True 1579 )

AttributeError: 'Array' object has no attribute 'reshape' ```

MVCE confirmation

• [X] Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• [X] Complete example — the example is self-contained, including all data and the text of any traceback.
• [X] Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• [X] New issue — a search of GitHub Issues suggests this is not a duplicate.
• [X] Recent environment — the issue occurs with the latest version of xarray and its dependencies.

Relevant log output

No response

Anything else we need to know?

It fails on the arr.reshape call, because the array API standard has reshape be a function, not a method.

We do in fact have an array API-compatible version of reshape defined in duck_array_ops.py, it just apparently isn't yet used everywhere we call reshape.

https://github.com/pydata/xarray/blob/037a39e249e5387bc15de447c57bfd559fd5a574/xarray/core/duck_array_ops.py#L363

Environment

main branch of xarray, numpy 1.26.0