changes

pandas/core/indexes/range.py

@@ -67,7 +67,7 @@ class RangeIndex(Int64Index):
     _engine_type = libindex.Int64Engine
 
     # check whether self._data has benn called
-    _has_called_data = False  # type: bool
+    _cached_data = None  # type: np.ndarray
     # --------------------------------------------------------------------
     # Constructors
 
@@ -186,10 +186,12 @@ def _constructor(self):
         """ return the class to use for construction """
         return Int64Index
 
-    @cache_readonly
+    @property
     def _data(self):
-        self._has_called_data = True
-        return np.arange(self._start, self._stop, self._step, dtype=np.int64)
+        if self._cached_data is None:
+            self._cached_data = np.arange(self._start, self._stop, self._step,
+                                          dtype=np.int64)
+        return self._cached_data
 
     @cache_readonly
     def _int64index(self):
@@ -223,7 +225,7 @@ def _format_data(self, name=None):
         return None
 
     def _format_with_header(self, header, na_rep='NaN', **kwargs):
-        return header + [pprint_thing(x) for x in self._range]
+        return header + list(map(pprint_thing, self._range))
 
     # --------------------------------------------------------------------
     @property

pandas/tests/indexes/test_range.py

@@ -241,35 +241,40 @@ def test_view(self):
     def test_dtype(self):
         assert self.index.dtype == np.int64
 
-    def test_has_called_data(self):
-        # Calling RangeIndex._data caches a array of the same length.
-        # This tests whether RangeIndex._data has been called by doing methods
+    def test_cached_data(self):
+        # Calling RangeIndex._data caches an int64 array of the same length at
+        # self._cached_data. This tests whether _cached_data has been set.
         idx = RangeIndex(0, 100, 10)
-        assert idx._has_called_data is False
+
+        assert idx._cached_data is None
 
         repr(idx)
-        assert idx._has_called_data is False
+        assert idx._cached_data is None
 
         str(idx)
-        assert idx._has_called_data is False
+        assert idx._cached_data is None
 
         idx.get_loc(20)
-        assert idx._has_called_data is False
+        assert idx._cached_data is None
 
         df = pd.DataFrame({'a': range(10)}, index=idx)
 
         df.loc[50]
-        assert idx._has_called_data is False
+        assert idx._cached_data is None
 
         with pytest.raises(KeyError):
             df.loc[51]
-        assert idx._has_called_data is False
+        assert idx._cached_data is None
 
         df.loc[10:50]
-        assert idx._has_called_data is False
+        assert idx._cached_data is None
 
         df.iloc[5:10]
-        assert idx._has_called_data is False
+        assert idx._cached_data is None
+
+        # actually calling data._data
+        assert isinstance(idx._data, np.ndarray)
+        assert isinstance(idx._cached_data, np.ndarray)
 
     def test_is_monotonic(self):
         assert self.index.is_monotonic is True