BUG: fixed bug where None would appear as 'None' (#57702)

pandas/core/arrays/numpy_.py

@@ -124,22 +124,20 @@ def _from_sequence(
         # None]"; expected "Union[dtype[Any], None, type, _SupportsDType, str,
         # Union[Tuple[Any, int], Tuple[Any, Union[int, Sequence[int]]], List[Any],
         # _DTypeDict, Tuple[Any, Any]]]"
-        if (None not in scalars):
+        if None not in scalars:
             result = np.asarray(scalars, dtype=dtype)
         else:
             try:
-                scalars_not_none=[item for item in scalars if item is not None]
-            except:
-                raise ValueError("NumpyExtensionArray must be 1-dimensional")
-            indexes_not_none=[]
-            indexed_data=[None]* len(scalars)
-            scalars_not_none_casted=np.asarray(scalars_not_none, dtype=dtype)
-            for i in range(len(scalars)):
-                if scalars[i] is not None:
-                    indexes_not_none.append(i)
+                scalars_not_none = [item for item in scalars if item is not None]
+            except Exception as err:
+                raise ValueError("NumpyExtensionArray must be 1-dimensional") from err
+            indexes_not_none = []
+            indexed_data = [None] * len(scalars)
+            scalars_not_none_casted = np.asarray(scalars_not_none, dtype=dtype)
+            indexes_not_none = [i for i, item in enumerate(scalars) if item is not None]
             for i in range(len(scalars_not_none)):
-                indexed_data[indexes_not_none[i]]=scalars_not_none_casted[i]
-            result=np.asarray(indexed_data, dtype="object")
+                indexed_data[indexes_not_none[i]] = scalars_not_none_casted[i]
+            result = np.asarray(indexed_data, dtype="object")
         if (
             result.ndim > 1
             and not hasattr(scalars, "dtype")

pandas/tests/arrays/numpy_/test_numpy.py

@@ -123,12 +123,14 @@ def test_from_sequence_dtype():
     result = NumpyExtensionArray._from_sequence(arr, dtype="uint64")
     expected = NumpyExtensionArray(np.array([1, 2, 3], dtype="uint64"))
     tm.assert_extension_array_equal(result, expected)
-
+
+
 def test_from_sequence_with_none():
-    result=pd.array([1, None], dtype=str)
-    expected=pd.array(['1', None], dtype="object")
+    result = pd.array([1, None], dtype=str)
+    expected = pd.array(["1", None], dtype="object")
     tm.assert_extension_array_equal(result, expected)
 
+
 def test_constructor_copy():
     arr = np.array([0, 1])
     result = NumpyExtensionArray(arr, copy=True)

pandas/tests/frame/test_constructors.py

@@ -1273,11 +1273,10 @@ def test_constructor_list_of_lists(self, using_infer_string):
 
     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
+        arr[0] = [1, 2]
+        arr[1] = [2, 4]
 
         df = DataFrame(arr)
         expected = DataFrame(pd.array(arr))