Refactor the code to extract test_value from different types of variables.

theano/gof/op.py

@@ -308,6 +308,28 @@ class PureOp(object):
         """
         raise utils.MethodNotDefined("make_node", type(self), self.__class__.__name__)
 
+    @classmethod
+    def _get_test_value(cls, v):
+        """
+        Extract test value from variable v. Raises AttributeError if there is none.
+
+        For a Constant, the test value is v.value.
+        For a Shared variable, it is the internal value.
+        For another Variable, it is the content of v.tag.test_value.
+        """
+        # avoid circular import
+        from theano.compile.sharedvalue import SharedVariable
+
+        if isinstance(v, graph.Constant):
+            return v.value
+        elif isinstance(v, SharedVariable):
+            return v.get_value(borrow=True, return_internal_type=True)
+        elif isinstance(v, graph.Variable) and hasattr(v.tag, 'test_value'):
+            # ensure that the test value is correct
+            return v.type.filter(v.tag.test_value)
+
+        raise AttributeError('%s has not test value' % v)
+
     def __call__(self, *inputs, **kwargs):
         """Optional: Return some or all output[s] of `make_node`.
 
@@ -329,21 +351,14 @@ class PureOp(object):
         self.add_tag_trace(node)
 
         if config.compute_test_value != 'off':
-            # avoid circular import
-            from theano.compile.sharedvalue import SharedVariable
             run_perform = True
 
             # build test input-values
             input_vals = []
             for i, ins in enumerate(node.inputs):
-                if isinstance(ins, graph.Constant):
-                    input_vals.append(ins.value)
-                elif isinstance(ins,SharedVariable):
-                    input_vals.append(ins.get_value(borrow=True, return_internal_type=True))
-                elif isinstance(ins,graph.Variable) and hasattr(ins.tag, 'test_value'):
-                    # ensure that the test value is correct
-                    input_vals.append(ins.type.filter(ins.tag.test_value))
-                else:
+                try:
+                    input_vals.append(self._get_test_value(ins))
+                except AttributeError:
                     # no test-value was specified, act accordingly
                     if config.compute_test_value == 'warn':
                         warnings.warn('Warning, Cannot compute test value: input %i (%s) of Op %s missing default value' % (i, ins, node), stacklevel=2)
@@ -373,7 +388,7 @@ class PureOp(object):
                 try:
                     node.op.perform(node, input_vals, output_storage)
 
-                    # add 'test_value' to output tags, so that downstream ops can use these
+                    # add 'test_value' to output tag, so that downstream ops can use these
                     # numerical values as inputs to their perform method.
                     for (outval, node_output) in zip(output_storage, node.outputs):
                         node_output.tag.test_value = outval[0]