rok commented on code in PR #50203:
URL: https://github.com/apache/arrow/pull/50203#discussion_r3459255332


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python/pyarrow/src/arrow/python/python_to_arrow.cc:
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@@ -908,8 +908,20 @@ class PyListConverter : public ListConverter<T, 
PyConverter, PyConverterTrait> {
 
   Status AppendNdarray(PyObject* value) {
     PyArrayObject* ndarray = reinterpret_cast<PyArrayObject*>(value);
+    OwnedRef flattened;
     if (PyArray_NDIM(ndarray) != 1) {
-      return Status::Invalid("Can only convert 1-dimensional array values");
+      // GH-49644: a fixed-size list (e.g. the storage of a fixed-shape tensor)
+      // can be built from a multi-dimensional array by flattening it in C
+      // order. The total number of elements must still match the list size,
+      // which the builder validates below. 0-dimensional arrays and
+      // variable-sized lists remain restricted to 1-dimensional values.
+      if (PyArray_NDIM(ndarray) < 2 || this->list_type_->id() != 
Type::FIXED_SIZE_LIST) {
+        return Status::Invalid("Can only convert 1-dimensional array values");
+      }
+      flattened.reset(PyArray_Ravel(ndarray, NPY_CORDER));
+      RETURN_IF_PYERROR();
+      value = flattened.obj();
+      ndarray = reinterpret_cast<PyArrayObject*>(value);
     }
     if (PyArray_ISBYTESWAPPED(ndarray)) {

Review Comment:
   I wonder how `PyArray_Ravel` behaves in big-endian situations? I imagine it 
would return the correct result but we can't really test anyway. Output would 
likely be `PyArray_ISBYTESWAPPED(ndarray) == true`  so this would fail and the 
computation above would be done in vain.
   @aboderinsamuel please move the `if (PyArray_ISBYTESWAPPED(ndarray))` block 
above the `if (PyArray_NDIM(ndarray) != 1)` block.



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