* top-level Variable class raises NotImplementedError when trying using comparison operators

theano/gof/graph.py

@@ -299,6 +299,15 @@ class Variable(utils.object2):
         cp = self.__class__(self.type, None, None, self.name)
         cp.tag = copy(self.tag)
         return cp
+    
+    def __lt__(self,other): 
+        raise NotImplementedError('Subclasses of Variable must implement __lt__')
+    def __le__(self,other): 
+        raise NotImplementedError('Subclasses of Variable must implement __le__')
+    def __gt__(self,other): 
+        raise NotImplementedError('Subclasses of Variable must implement __gt__')
+    def __ge__(self,other): 
+        raise NotImplementedError('Subclasses of Variable must implement __ge__')
 
 class Value(Variable):
     """

theano/tensor/basic.py

@@ -1130,7 +1130,7 @@ class _tensor_py_operators:
     def get_constant_value(self):
         return get_constant_value(self)
 
-class TensorVariable(Variable, _tensor_py_operators):
+class TensorVariable(_tensor_py_operators, Variable):
     """Subclass to add the tensor operators to the basic `Variable` class."""
 TensorType.Variable = TensorVariable
 
@@ -1162,7 +1162,7 @@ class TensorConstantSignature(tuple):
     sum = property(_get_sum)
 
 
-class TensorConstant(Constant, _tensor_py_operators):
+class TensorConstant(_tensor_py_operators, Constant):
     """Subclass to add the tensor operators to the basic `Constant` class.
 
     To create a TensorConstant, use the `constant` function in this module.
@@ -1171,7 +1171,7 @@ class TensorConstant(Constant, _tensor_py_operators):
         return TensorConstantSignature((self.type, self.data))
 TensorType.Constant = TensorConstant
 
-class TensorValue(Value, _tensor_py_operators):
+class TensorValue(_tensor_py_operators, Value):
     """Subclass to add the tensor operators to the basic `Value` class.
 
     To create a TensorValue, use the `value` function in this module.