BUG: DataFrame(nested_object_ndarray) match DataFrame(nested_pandas_array) GH#43986

Author: jbrockmendel

pandas/core/apply.py

@@ -57,7 +57,6 @@
 )
 import pandas.core.common as com
 from pandas.core.construction import (
-    array as pd_array,
     create_series_with_explicit_dtype,
     ensure_wrapped_if_datetimelike,
 )
@@ -1144,7 +1143,8 @@ def apply_standard(self) -> DataFrame | Series:
         if len(mapped) and isinstance(mapped[0], ABCSeries):
             # GH 25959 use pd.array instead of tolist
             # so extension arrays can be used
-            return obj._constructor_expanddim(pd_array(mapped), index=obj.index)
+            # GH#43986 Need to do list(mapped) in order to get treated as nested
+            return obj._constructor_expanddim(list(mapped), index=obj.index)
         else:
             return obj._constructor(mapped, index=obj.index).__finalize__(
                 obj, method="apply"

pandas/core/frame.py

@@ -666,7 +666,7 @@ def __init__(
                     typ=manager,
                 )
 
-        elif isinstance(data, (np.ndarray, Series, Index)):
+        elif isinstance(data, (np.ndarray, Series, Index, ExtensionArray)):
             if data.dtype.names:
                 # i.e. numpy structured array
                 data = cast(np.ndarray, data)

pandas/tests/frame/test_constructors.py

@@ -1305,6 +1305,20 @@ def test_constructor_list_of_lists(self):
         result = DataFrame(data)
         tm.assert_frame_equal(result, expected)
 
+    def test_nested_pandasarray_matches_nested_ndarray(self):
+        # GH#43986
+        ser = Series([1, 2])
+
+        arr = np.array([None, None], dtype=object)
+        arr[0] = ser
+        arr[1] = ser * 2
+
+        df = DataFrame(arr)
+        expected = DataFrame(pd.array(arr))
+        tm.assert_frame_equal(df, expected)
+        assert df.shape == (2, 1)
+        tm.assert_numpy_array_equal(df[0].values, arr)
+
     def test_constructor_list_like_data_nested_list_column(self):
         # GH 32173
         arrays = [list("abcd"), list("cdef")]