[python] Add worldEntity util (#1308)

Signed-off-by: Louise Poubel <[email protected]>

examples/scripts/python_api/README.md

@@ -0,0 +1,6 @@
+# Gazebo Python API
+
+This example shows how to use Gazebo's Python API.
+
+For more information, see the
+[Python interfaces](https://ignitionrobotics.org/api/gazebo/6.4/python_interfaces.html) tutorial.

examples/python/testFixture.py → examples/scripts/python_api/testFixture.py

@@ -20,13 +20,13 @@
 #
 # Now you can run the example:
 #
-# python3 examples/python/helperFixture.py
+# python3 examples/scripts/python_api/helperFixture.py
 
 import os
 import time
 
 from ignition.common import set_verbosity
-from ignition.gazebo import TestFixture, World
+from ignition.gazebo import TestFixture, World, world_entity
 from ignition.math import Vector3d
 from sdformat import Element
 
@@ -39,24 +39,36 @@
 post_iterations = 0
 iterations = 0
 pre_iterations = 0
-
-
-def on_post_udpate_cb(_info, _ecm):
-    global post_iterations
-    post_iterations += 1
-    # print(_info.sim_time)
+first_iteration = True
 
 
 def on_pre_udpate_cb(_info, _ecm):
     global pre_iterations
+    global first_iteration
     pre_iterations += 1
+    if first_iteration:
+        first_iteration = False
+        world_e = world_entity(_ecm);
+        print('World entity is ', world_e)
+        w = World(world_e)
+        v = w.gravity(_ecm)
+        print('Gravity ', v)
+        modelEntity = w.model_by_name(_ecm, 'falling')
+        print('Entity for falling model is: ', modelEntity)
 
 
 def on_udpate_cb(_info, _ecm):
     global iterations
     iterations += 1
 
 
+def on_post_udpate_cb(_info, _ecm):
+    global post_iterations
+    post_iterations += 1
+    if _info.sim_time.seconds == 1:
+        print('Post update sim time: ', _info.sim_time)
+
+
 helper.on_post_update(on_post_udpate_cb)
 helper.on_update(on_udpate_cb)
 helper.on_pre_update(on_pre_udpate_cb)

include/ignition/gazebo/EventManager.hh

@@ -140,8 +140,6 @@ namespace ignition
                  }
                };
 
-      /// This was originally a unique_ptr, but pybind11 was failing because it
-      /// was not able to copy the class
       /// \brief Container of used signals.
       private: std::unordered_map<TypeInfoRef,
                                   std::unique_ptr<ignition::common::Event>,

python/CMakeLists.txt

@@ -46,6 +46,7 @@ pybind11_add_module(gazebo SHARED
   src/ignition/gazebo/Server.cc
   src/ignition/gazebo/ServerConfig.cc
   src/ignition/gazebo/UpdateInfo.cc
+  src/ignition/gazebo/Util.cc
   src/ignition/gazebo/World.cc
 )
 

python/src/ignition/gazebo/Util.cc

@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2021 Open Source Robotics Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+#include <pybind11/pybind11.h>
+#include <pybind11/stl.h>
+
+#include <iostream>
+
+#include <ignition/gazebo/Util.hh>
+#include "Util.hh"
+
+namespace ignition
+{
+namespace gazebo
+{
+namespace python
+{
+void defineGazeboUtil(pybind11::module &_module)
+{
+  _module.def("world_entity",
+      pybind11::overload_cast<const EntityComponentManager &>(
+      &ignition::gazebo::worldEntity),
+      "Get the first world entity that's found.");
+}
+}  // namespace python
+}  // namespace gazebo
+}  // namespace ignition

python/src/ignition/gazebo/Util.hh

@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2021 Open Source Robotics Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef IGNITION_GAZEBO_PYTHON__UTIL_HH_
+#define IGNITION_GAZEBO_PYTHON__UTIL_HH_
+
+#include <pybind11/pybind11.h>
+
+#include <ignition/gazebo/Util.hh>
+
+namespace ignition
+{
+namespace gazebo
+{
+namespace python
+{
+/// Define a pybind11 wrapper for a ignition::gazebo::Util
+/// \param[in] _module a pybind11 module to add the definition to
+void defineGazeboUtil(pybind11::module &_module);
+}  // namespace python
+}  // namespace gazebo
+}  // namespace ignition
+
+#endif  // IGNITION_GAZEBO_PYTHON__WORLD_HH_

python/src/ignition/gazebo/_ignition_gazebo_pybind11.cc

@@ -22,6 +22,7 @@
 #include "ServerConfig.hh"
 #include "TestFixture.hh"
 #include "UpdateInfo.hh"
+#include "Util.hh"
 #include "World.hh"
 
 PYBIND11_MODULE(gazebo, m) {
@@ -34,4 +35,5 @@ PYBIND11_MODULE(gazebo, m) {
   ignition::gazebo::python::defineGazeboTestFixture(m);
   ignition::gazebo::python::defineGazeboUpdateInfo(m);
   ignition::gazebo::python::defineGazeboWorld(m);
+  ignition::gazebo::python::defineGazeboUtil(m);
 }

python/test/testFixture_TEST.py

@@ -17,7 +17,7 @@
 import unittest
 
 from ignition.common import set_verbosity
-from ignition.gazebo import TestFixture, World
+from ignition.gazebo import TestFixture, World, world_entity
 from ignition.math import Vector3d
 from sdformat import Element
 
@@ -40,6 +40,11 @@ def on_post_udpate_cb(_info, _ecm):
         def on_pre_udpate_cb(_info, _ecm):
             global pre_iterations
             pre_iterations += 1
+            world_e = world_entity(_ecm);
+            self.assertEqual(1, world_e)
+            w = World(world_e)
+            v = w.gravity(_ecm)
+            self.assertEqual(Vector3d(0, 0, -9.8), v)
 
         def on_udpate_cb(_info, _ecm):
             global iterations

tutorials/python_interfaces.md

@@ -14,7 +14,7 @@ step simulation and check entities and components.
     helper = HelperFixture(os.path.join(file_path, 'gravity.sdf'))
     ```
 
- - **Step 2**: Write your `configure`, `pretupdate`, `update` or `postupdate` code:
+ - **Step 2**: Write your `pretupdate`, `update` or `postupdate` code:
     ```python
     def on_post_udpate_cb(_info, _ecm):
       # <your code here>
@@ -41,18 +41,21 @@ step simulation and check entities and components.
 
 # Run the example
 
-In the [examples/python](https://github.com/ignitionrobotics/ign-gazebo/blob/ign-gazebo6/examples/python) folder there is a Python script
-shows make use of this API. If you compiled Ignition Gazebo from source you should modify your `PYTHONPATH`:
+In the
+[examples/scripts/python_api](https://github.com/ignitionrobotics/ign-gazebo/blob/ign-gazebo6/examples/scripts/python_api)
+folder there is a Python script that shows how to make use of this API.
 
-```bash
-export PYTHONPATH=$PYTHONPATH:<path to ws>/install/lib/python
-```
+> If you compiled Ignition Gazebo from source you should modify your `PYTHONPATH`:
+>
+>  ```bash
+>  export PYTHONPATH=$PYTHONPATH:<path to ws>/install/lib/python
+>    ```
 
 Now you can run the example:
 
 ```bash
-$ python3 examples/python/helperFixture.py
-[Msg] Loading SDF world file[/home/ahcorde/ignition_fortress/src/ign-gazebo/examples/python/gravity.sdf].
+$ python3 examples/scripts/python_api/helperFixture.py
+[Msg] Loading SDF world file[/home/ahcorde/ignition_fortress/src/ign-gazebo/examples/scripts/python_api/gravity.sdf].
 [Dbg] [Physics.cc:789] Loaded [ignition::physics::dartsim::Plugin] from library [/home/ahcorde/ignition_fortress/install/lib/ign-physics-5/engine-plugins/libignition-physics-dartsim-plugin.so]
 [Dbg] [SimulationRunner.cc:909] Loaded system [ignition::gazebo::systems::Physics] for entity [1]
 [Msg] Loaded level [3]