Give the python layer parameter/weight blobs.

python/caffe/_caffe.cpp

@@ -190,6 +190,21 @@ bp::object Blob_Reshape(bp::tuple args, bp::dict kwargs) {
   return bp::object();
 }
 
+bp::object BlobVec_add_blob(bp::tuple args, bp::dict kwargs) {
+  if (bp::len(kwargs) > 0) {
+    throw std::runtime_error("BlobVec.add_blob takes no kwargs");
+  }
+  typedef vector<shared_ptr<Blob<Dtype> > > BlobVec;
+  BlobVec* self = bp::extract<BlobVec*>(args[0]);
+  vector<int> shape(bp::len(args) - 1);
+  for (int i = 1; i < bp::len(args); ++i) {
+    shape[i - 1] = bp::extract<int>(args[i]);
+  }
+  self->push_back(shared_ptr<Blob<Dtype> >(new Blob<Dtype>(shape)));
+  // We need to explicitly return None to use bp::raw_function.
+  return bp::object();
+}
+
 BOOST_PYTHON_MEMBER_FUNCTION_OVERLOADS(SolveOverloads, Solve, 0, 1);
 
 BOOST_PYTHON_MODULE(_caffe) {
@@ -288,7 +303,8 @@ BOOST_PYTHON_MODULE(_caffe) {
 
   // vector wrappers for all the vector types we use
   bp::class_<vector<shared_ptr<Blob<Dtype> > > >("BlobVec")
-    .def(bp::vector_indexing_suite<vector<shared_ptr<Blob<Dtype> > >, true>());
+    .def(bp::vector_indexing_suite<vector<shared_ptr<Blob<Dtype> > >, true>())
+    .def("add_blob", bp::raw_function(&BlobVec_add_blob));
   bp::class_<vector<Blob<Dtype>*> >("RawBlobVec")
     .def(bp::vector_indexing_suite<vector<Blob<Dtype>*>, true>());
   bp::class_<vector<shared_ptr<Layer<Dtype> > > >("LayerVec")

python/caffe/test/test_python_layer.py

@@ -28,6 +28,21 @@ class ExceptionLayer(caffe.Layer):
     def setup(self, bottom, top):
         raise RuntimeError
 
+class ParameterLayer(caffe.Layer):
+    """A layer that just multiplies by ten"""
+
+    def setup(self, bottom, top):
+        self.blobs.add_blob(1)
+        self.blobs[0].data[0] = 0
+
+    def reshape(self, bottom, top):
+        top[0].reshape(*bottom[0].data.shape)
+
+    def forward(self, bottom, top):
+        pass
+
+    def backward(self, top, propagate_down, bottom):
+        self.blobs[0].diff[0] = 1
 
 def python_net_file():
     with tempfile.NamedTemporaryFile(mode='w+', delete=False) as f:
@@ -52,6 +67,16 @@ def exception_net_file():
         return f.name
 
 
+def parameter_net_file():
+    with tempfile.NamedTemporaryFile(mode='w+', delete=False) as f:
+        f.write("""name: 'pythonnet' force_backward: true
+        input: 'data' input_shape { dim: 10 dim: 9 dim: 8 }
+        layer { type: 'Python' name: 'layer' bottom: 'data' top: 'top'
+          python_param { module: 'test_python_layer' layer: 'ParameterLayer' } }
+          """)
+        return f.name
+
+
 class TestPythonLayer(unittest.TestCase):
     def setUp(self):
         net_file = python_net_file()
@@ -84,3 +109,32 @@ def test_exception(self):
         net_file = exception_net_file()
         self.assertRaises(RuntimeError, caffe.Net, net_file, caffe.TEST)
         os.remove(net_file)
+
+    def test_parameter(self):
+        net_file = parameter_net_file()
+        net = caffe.Net(net_file, caffe.TRAIN)
+        # Test forward and backward
+        net.forward()
+        net.backward()
+        layer = net.layers[list(net._layer_names).index('layer')]
+        self.assertEqual(layer.blobs[0].data[0], 0)
+        self.assertEqual(layer.blobs[0].diff[0], 1)
+        layer.blobs[0].data[0] += layer.blobs[0].diff[0]
+        self.assertEqual(layer.blobs[0].data[0], 1)
+
+        # Test saving and loading
+        h, caffemodel_file = tempfile.mkstemp()
+        net.save(caffemodel_file)
+        layer.blobs[0].data[0] = -1
+        self.assertEqual(layer.blobs[0].data[0], -1)
+        net.copy_from(caffemodel_file)
+        self.assertEqual(layer.blobs[0].data[0], 1)
+        os.remove(caffemodel_file)
+        
+        # Test weight sharing
+        net2 = caffe.Net(net_file, caffe.TRAIN)
+        net2.share_with(net)
+        layer = net.layers[list(net2._layer_names).index('layer')]
+        self.assertEqual(layer.blobs[0].data[0], 1)
+
+        os.remove(net_file)