BUG/API: Indexes on empty frames/series should be RangeIndex, are Index[object]

Author: Terji Petersen

pandas/core/frame.py

@@ -2232,8 +2232,7 @@ def maybe_reorder(
 
             result_index = None
             if len(arrays) == 0 and index is None and length == 0:
-                # for backward compat use an object Index instead of RangeIndex
-                result_index = Index([])
+                result_index = default_index(0)
 
             arrays, arr_columns = reorder_arrays(arrays, arr_columns, columns, length)
             return arrays, arr_columns, result_index

pandas/core/internals/construction.py

@@ -435,7 +435,7 @@ def dict_to_mgr(
 
     else:
         keys = list(data.keys())
-        columns = Index(keys)
+        columns = Index(keys) if len(keys) else default_index(0)
         arrays = [com.maybe_iterable_to_list(data[k]) for k in keys]
         arrays = [arr if not isinstance(arr, Index) else arr._data for arr in arrays]
 
@@ -582,7 +582,7 @@ def _extract_index(data) -> Index:
     """
     index = None
     if len(data) == 0:
-        index = Index([])
+        index = default_index(0)
     else:
         raw_lengths = []
         indexes: list[list[Hashable] | Index] = []

pandas/core/series.py

@@ -512,7 +512,7 @@ def _init_dict(
                 values = []
             keys = index
         else:
-            keys, values = (), []
+            keys, values = default_index(0), []
 
         # Input is now list-like, so rely on "standard" construction: