FIX: replaces ndim check with ABC subclass check

Author: deniederhut

Diff for: pandas/core/generic.py

@@ -28,7 +28,7 @@
     pandas_dtype)
 from pandas.core.dtypes.cast import maybe_promote, maybe_upcast_putmask
 from pandas.core.dtypes.missing import isnull, notnull
-from pandas.core.dtypes.generic import ABCSeries, ABCPanel
+from pandas.core.dtypes.generic import ABCSeries, ABCPanel, ABCDataFrame
 
 from pandas.core.common import (_values_from_object,
                                 _maybe_box_datetimelike,
@@ -3278,7 +3278,7 @@ def __setattr__(self, name, value):
                 else:
                     object.__setattr__(self, name, value)
             except (AttributeError, TypeError):
-                if (self.ndim > 1) and (is_list_like(value)):
+                if isinstance(self, ABCDataFrame) and (is_list_like(value)):
                     warnings.warn("Pandas doesn't allow Series to be assigned "
                                   "into nonexistent columns - see "
                                   "https://pandas.pydata.org/pandas-docs/"