API: Series.str wont' raise and now returns None (GH6106)

pandas/core/generic.py

@@ -79,7 +79,7 @@ class NDFrame(PandasObject):
     copy : boolean, default False
     """
     _internal_names = ['_data', '_cacher', '_item_cache', '_cache',
-                       'is_copy', '_subtyp', '_index', '_default_kind',
+                       'is_copy', 'str', '_subtyp', '_index', '_default_kind',
                        '_default_fill_value','__array_struct__','__array_interface__']
     _internal_names_set = set(_internal_names)
     _metadata = []
@@ -616,7 +616,7 @@ def equals(self, other):
         if not isinstance(other, self._constructor):
             return False
         return self._data.equals(other._data)
-            
+
     #----------------------------------------------------------------------
     # Iteration
 

pandas/src/properties.pyx

@@ -22,7 +22,10 @@ cdef class cache_readonly(object):
 
         cache = getattr(obj, '_cache', None)
         if cache is None:
-            cache = obj._cache = {}
+            try:
+                cache = obj._cache = {}
+            except (AttributeError):
+                return
 
         if PyDict_Contains(cache, self.name):
             # not necessary to Py_INCREF
@@ -40,10 +43,13 @@ cdef class cache_readonly(object):
         # Get the cache or set a default one if needed
         cache = getattr(obj, '_cache', None)
         if cache is None:
-            cache = obj._cache = {}
+            try:
+                cache = obj._cache = {}
+            except (AttributeError):
+                return
 
         PyDict_SetItem(cache, self.name, value)
-            
+
 cdef class AxisProperty(object):
     cdef:
         Py_ssize_t axis

pandas/tests/test_strings.py

@@ -29,6 +29,11 @@ class TestStringMethods(tm.TestCase):
 
     _multiprocess_can_split_ = True
 
+    def test_api(self):
+
+        # GH 6106
+        self.assert_(Series.str is None)
+
     def test_iter(self):
         # GH3638
         strs = 'google', 'wikimedia', 'wikipedia', 'wikitravel'