Merge pull request #4470 from nouiz/fix_slice_symbol

theano/tensor/tests/test_subtensor.py

@@ -329,6 +329,14 @@ class T_subtensor(unittest.TestCase, utt.TestOptimizationMixin):
         x = numpy.arange(100).reshape((5, 5, 4))
         numpy.allclose(res, x[[slice(1, -1)] * x.ndim])
 
+    def test_slice_symbol(self):
+        x = self.shared(numpy.random.rand(5, 4).astype(self.dtype))
+        y = self.shared(numpy.random.rand(1, 2, 3).astype(self.dtype))
+        o = x[:y.shape[0], None, :]
+        f = theano.function([], o, mode=self.mode)
+        ret = f()
+        assert ret.shape == (1, 1, 4)
+
     def test_newaxis(self):
         """
         newaxis support comes from logic in the __getitem__ of TensorType

theano/tensor/var.py

@@ -524,8 +524,17 @@ class _tensor_py_operators(object):
                         counter += 1
                         new_args.append(arg)
                 view = self.dimshuffle(pattern)
-                check_rval = [arg == slice(None, None, None) for arg in new_args]
-                if all(check_rval) == True:
+                full_slices = True
+                for arg in new_args:
+                    # We can't do arg == slice(None, None, None) as in
+                    # Python 2.7, this call __lt__ if we have a slice
+                    # with some symbolic variable.
+                    if not (isinstance(arg, slice) and
+                            arg.start is None and
+                            arg.stop is None and
+                            arg.step is None):
+                        full_slices = False
+                if full_slices:
                     return view
                 else:
                     return view.__getitem__(tuple(new_args))