RangeIndex as default index

pandas/core/api.py

@@ -8,7 +8,7 @@
 from pandas.core.categorical import Categorical
 from pandas.core.groupby import Grouper
 from pandas.core.format import set_eng_float_format
-from pandas.core.index import Index, CategoricalIndex, Int64Index, Float64Index, MultiIndex
+from pandas.core.index import Index, CategoricalIndex, Int64Index, RangeIndex, Float64Index, MultiIndex
 
 from pandas.core.series import Series, TimeSeries
 from pandas.core.frame import DataFrame

pandas/core/common.py

@@ -86,6 +86,7 @@ def _check(cls, inst):
 ABCCategoricalIndex = create_pandas_abc_type("ABCCategoricalIndex", "_typ", ("categoricalindex",))
 ABCIndexClass = create_pandas_abc_type("ABCIndexClass", "_typ", ("index",
                                                                  "int64index",
+                                                                 "rangeindex",
                                                                  "float64index",
                                                                  "multiindex",
                                                                  "datetimeindex",
@@ -2142,9 +2143,8 @@ def is_bool_indexer(key):
 
 
 def _default_index(n):
-    from pandas.core.index import Int64Index
-    values = np.arange(n, dtype=np.int64)
-    result = Int64Index(values,name=None)
+    from pandas.core.index import RangeIndex
+    result = RangeIndex(0, int(n), name=None)
     result.is_unique = True
     return result
 
@@ -2498,6 +2498,11 @@ def is_integer_dtype(arr_or_dtype):
             not issubclass(tipo, (np.datetime64, np.timedelta64)))
 
 
+def is_int64_dtype(arr_or_dtype):
+    tipo = _get_dtype_type(arr_or_dtype)
+    return issubclass(tipo, np.int64)
+
+
 def is_int_or_datetime_dtype(arr_or_dtype):
     tipo = _get_dtype_type(arr_or_dtype)
     return (issubclass(tipo, np.integer) or

pandas/core/frame.py

@@ -4826,7 +4826,7 @@ def extract_index(data):
                            % (lengths[0], len(index)))
                     raise ValueError(msg)
             else:
-                index = Index(np.arange(lengths[0]))
+                index = _default_index(lengths[0])
 
     return _ensure_index(index)
 
@@ -5043,11 +5043,11 @@ def convert(arr):
 
 
 def _get_names_from_index(data):
-    index = lrange(len(data))
     has_some_name = any([getattr(s, 'name', None) is not None for s in data])
     if not has_some_name:
-        return index
+        return _default_index(len(data))
 
+    index = lrange(len(data))
     count = 0
     for i, s in enumerate(data):
         n = getattr(s, 'name', None)