REGR: bug in moments when using bottleneck

closes #16116

Author: jreback

pandas/core/nanops.py

@@ -381,6 +381,7 @@ def nanstd(values, axis=None, skipna=True, ddof=1):
 @bottleneck_switch(ddof=1)
 def nanvar(values, axis=None, skipna=True, ddof=1):
 
+    values = _values_from_object(values)
     dtype = values.dtype
     mask = isnull(values)
     if is_any_int_dtype(values):

pandas/tests/frame/test_analytics.py

@@ -591,6 +591,22 @@ def test_numeric_only_flag(self):
             pytest.raises(TypeError, lambda: getattr(df2, meth)(
                 axis=1, numeric_only=False))
 
+    def test_mixed_ops(self):
+        # GH 16116
+        df = DataFrame({'int': [1, 2, 3, 4],
+                        'float': [1., 2., 3., 4.],
+                        'str': ['a', 'b', 'c', 'd']})
+
+        for op in ['mean', 'std']:
+            result = getattr(df, op)()
+            assert len(result) == 2
+
+            if nanops._USE_BOTTLENECK:
+                nanops._USE_BOTTLENECK = False
+                result = getattr(df, op)()
+                assert len(result) == 2
+                nanops._USE_BOTTLENECK = True
+
     def test_cumsum(self):
         self.tsframe.loc[5:10, 0] = nan
         self.tsframe.loc[10:15, 1] = nan