Check if data type is slice before comparing with slice(None)

Author: chilin0525

pandas/core/internals/managers.py

@@ -572,12 +572,10 @@ def setitem(self, indexer, value) -> Self:
                         0, blk_loc, values
                     )
                     # first block equals values
-                    is_full_column_selection = indexer[1] == slice(None)
-                    col_indexer = (
-                        slice(None)
-                        if is_full_column_selection
-                        else np.arange(len(blk_loc))
-                    )
+                    if isinstance(indexer[1], slice) and indexer[1] == slice(None):
+                        col_indexer = slice(None)
+                    else:
+                        col_indexer = np.arange(len(blk_loc))
                     self.blocks[0].setitem((indexer[0], col_indexer), value)
                     return self
             # No need to split if we either set all columns or on a single block