Expose Executor to Python (#4804)

* Expose Executor to Python

* Follow comments

paddle/pybind/CMakeLists.txt

 if(WITH_PYTHON)
   cc_library(paddle_pybind SHARED
     SRCS pybind.cc exception.cc protobuf.cc
-    DEPS pybind python backward proto_desc tensor_array paddle_memory
+    DEPS pybind python backward proto_desc tensor_array paddle_memory executor
     ${GLOB_OP_LIB})
 endif(WITH_PYTHON)

paddle/pybind/pybind.cc

@@ -15,6 +15,7 @@ limitations under the License. */
 #include "paddle/pybind/protobuf.h"
 
 #include "paddle/framework/backward.h"
+#include "paddle/framework/executor.h"
 #include "paddle/framework/lod_tensor.h"
 #include "paddle/framework/tensor_array.h"
 #include "paddle/operators/cond_op.h"
@@ -391,6 +392,14 @@ All parameter, weight, gradient are variables in Paddle.
              self.set_falsenet(net.Clone());
            });
 
+  py::class_<framework::Executor>(m, "Executor")
+      .def(py::init<std::vector<platform::Place> &>())
+      .def("run",
+           [](Executor &self, const ProgramDesc &program_desc, int block_id) {
+             framework::Scope &global_scope = GetGlobalScope();
+             self.Run(program_desc, &global_scope, block_id);
+           });
+
   m.def("unique_integer", UniqueIntegerGenerator);
 
   m.def("is_compile_gpu", IsCompileGPU);