BUG: modulo should not be commutative in general

Author: cpcloud

pandas/core/frame.py

@@ -874,7 +874,8 @@ def __contains__(self, key):
                                   default_axis=None, fill_zeros=np.inf)
     __rpow__ = _arith_method(lambda x, y: y ** x, '__rpow__',
                              default_axis=None)
-    __rmod__ = _arith_method(operator.mod, '__rmod__', default_axis=None, fill_zeros=np.nan)
+    __rmod__ = _arith_method(lambda x, y: y % x, '__rmod__', default_axis=None,
+                             fill_zeros=np.nan)
 
     # boolean operators
     __and__ = _arith_method(operator.and_, '__and__', '&')

pandas/core/series.py

@@ -1266,7 +1266,7 @@ def iteritems(self):
     __rtruediv__ = _arith_method(lambda x, y: y / x, '__truediv__', fill_zeros=np.inf)
     __rfloordiv__ = _arith_method(lambda x, y: y // x, '__floordiv__', fill_zeros=np.inf)
     __rpow__ = _arith_method(lambda x, y: y ** x, '__pow__')
-    __rmod__ = _arith_method(operator.mod, '__mod__', fill_zeros=np.nan)
+    __rmod__ = _arith_method(lambda x, y: y % x, '__mod__', fill_zeros=np.nan)
 
     # comparisons
     __gt__ = _comp_method(operator.gt, '__gt__')