rok commented on code in PR #50325:
URL: https://github.com/apache/arrow/pull/50325#discussion_r3528401021
##########
python/pyarrow/types.pxi:
##########
@@ -1969,6 +1969,11 @@ cdef class JsonType(BaseExtensionType):
return JsonScalar
+class _UuidPandasDtype:
+ def __from_arrow__(self, array):
+ return np.asarray(array.to_pylist(), dtype=object).reshape(1, -1)
Review Comment:
Wouldn't this make `UuidType.__from_arrow__` return a 2-D array to satisfy
old pandas `DataFrame` block construction, but the same hook is also used by
`Array.to_pandas()`, which expects 1-D data for pd.Series?
Perhaps a better fix is to keep `__from_arrow__` returning normal 1-D object
data, and handle the old pandas block-manager reshape only in the `DataFrame`
reconstruction path where 2-D block shape is
actually needed?
Something like:
```diff
diff --git a/python/pyarrow/types.pxi b/python/pyarrow/types.pxi
--- a/python/pyarrow/types.pxi
+++ b/python/pyarrow/types.pxi
@@ -1971,7 +1971,7 @@ cdef class JsonType(BaseExtensionType):
class _UuidPandasDtype:
def __from_arrow__(self, array):
- return np.asarray(array.to_pylist(), dtype=object).reshape(1, -1)
+ # Return a 1-D object array of uuid.UUID values (nulls become None).
+ # Per pandas' __from_arrow__ contract this is 1-D; the
table-to-blocks
+ # path reshapes it to the single-column block layout as needed.
+ return np.asarray(array.to_pylist(), dtype=object)
cdef class UuidType(BaseExtensionType):
diff --git a/python/pyarrow/pandas_compat.py
b/python/pyarrow/pandas_compat.py
--- a/python/pyarrow/pandas_compat.py
+++ b/python/pyarrow/pandas_compat.py
@@ -779,6 +779,13 @@ def _reconstruct_block(item, columns=None,
extension_columns=None,
if not hasattr(pandas_dtype, '__from_arrow__'):
raise ValueError("This column does not support to be converted "
"to a pandas ExtensionArray")
arr = pandas_dtype.__from_arrow__(arr)
+ if isinstance(arr, np.ndarray) and arr.ndim == 1:
+ # A plain (non-ExtensionArray) 1-D result — e.g. from the UUID
+ # extension type — must be reshaped to the (1, n) single-column
+ # block layout that make_block and create_dataframe_from_blocks
+ # expect. pandas ExtensionArrays are 1-D and handled directly,
so
+ # they are intentionally left untouched here.
+ arr = arr.reshape(1, -1)
else:
arr = block_arr
```
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