pymrpt broken in ros-noetic-mrpt2 in 2.9.0

[ihadzic]

ros-noetic-mrpt2 package (on Ubuntu 20.04) just got an update to 2.9.0 and pymrpt broke there. I have an import like this:

from pymrpt.poses import CPose3DPDFGaussian

and it pukes with this message:

from pymrpt.poses import CPose3DPDFGaussian
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'pymrpt'

This has worked fine in 2.8.0 and the bindings were found in /opt/ros/noetic/lib/python3/dist-packages/pymrpt.so. That file is gone in 2.9.0 but in instead what showed up that looks like should be Python binding are files under /opt/ros/noetic/lib/python3.8/site-packages/mrpt but that doesn't import and even if I try to hack my way into importing it doesn't look like a correct pymrpt module (it doesn't have poses submodule at all).

[jlblancoc]

Ok, I see. I have verified it on a u20.04 system with the latest packages from the ROS build farm for Noetic.

Two different things here:

1. python3 not finding the library. That's "easy" to hack away, as you probably have already done, either creating symlinks under /opt/ros/noetic/lib/python3/dist-packages (not recommended) or by temporarily adding:

    export PYTHONPATH=$PYTHONPATH:/opt/ros/noetic/lib/python3.8/site-packages/
   

2. With MRPT 2.9.0, there has been a massive change in the Python bindings: it formerly was hand-written and only exported part of the API. It's now automated via pybind11 and most parts of MRPT are now available via pymrpt. The names and such changed a bit, though.
   Please, see:

   • Examples like se3-poses-example.py or hwdriver-tao-imu-usb.py for a possible way to import the module (first few lines), and
   • The only (ugly) pydoc reference docs of all existing classes, modules and methods. If you use the interactive python3 interpreter, tab will help you to autocomplete, but I wasn't able to make Visual Studio Code to autocomplete pymrpt classes, and couldn't find the reason...

Any help with testing, improving, adding/correcting Python examples, etc. would be more than welcome, since we normally develop with the C++ libs and the python part is far less tested...

I'm leaving this ticket open to remember trying to fix the installation path of pymrpt in noetic.

[jlblancoc]

PS: I realized the logic to determine the install directory for pymrpt is inverted! python3 is used for ROS2, python3.X for ROS1, while it should be the other way around.
I'll fix it asap.

[jlblancoc]

The latest release v2.9.2 should fix these issues in ROS 1 and ROS 2, as well as in the PPA python3-pymrpt package.
Note there are now also a few examples online to help with code migration with former versions, hope it helps!

[ihadzic]

Thanks for fixing this. I am still struggling to find everything I need in the new API. Specifically, I need to go back and forth between ROS1 messages and MRPT types. In the old API I would use something like this:

p1mrpt = CPose3DPDFGaussian()
p1mrpt.from_ROS_PoseWithCovariance_msg(p1)

where p1 is PoseWithCovariance type from geometry_msgs.msg

In the new API, I understand I should use ros1bridge that is documented here:

https://docs.mrpt.org/reference/latest/group_mrpt_ros1bridge_grp.html

and call toROS and fromROS to do the conversion. Assuming that Python bindings follow the hierarchy that C++ follows, I would expect to find ros1bridge under pymrpt.mrpt, but I don't see it:

>>> from mrpt import pymrpt
>>> dir(pymrpt.mrpt)
['Clock', 'DEG2RAD', 'RAD2DEG', 'Stringifyable', 'TCallStackBackTrace', 'TCallStackEntry', 'WorkerThreadsPool', '__doc__', '__loader__', '__name__', '__package__', '__spec__', 'aligned_calloc', 'aligned_free', 'aligned_malloc', 'apps', 'bayes', 'callStackBackTrace', 'comms', 'config', 'containers', 'cpu', 'd2f', 'expr', 'f2u8', 'global_settings', 'graphs', 'gui', 'hwdrivers', 'hypot_fast', 'ignored_copy_ptr_mrpt_maps_COctoMapBase_octomap_ColorOcTree_octomap_ColorOcTreeNode_t', 'ignored_copy_ptr_mrpt_maps_COctoMapBase_octomap_OcTree_octomap_OcTreeNode_t', 'img', 'int_select_by_bytecount_1_t', 'int_select_by_bytecount_2_t', 'int_select_by_bytecount_3_t', 'int_select_by_bytecount_4_t', 'int_select_by_bytecount_8_t', 'io', 'keep_max', 'keep_min', 'kinematics', 'maps', 'math', 'nav', 'non_copiable_ptr_basic_void_t', 'obs', 'opengl', 'poses', 'ptr_cast_mrpt_serialization_CSerializable_t', 'random', 'round', 'rtti', 'safe_ptr_basic_mrpt_opengl_Scene_t', 'safe_ptr_basic_mrpt_rtti_TRuntimeClassId_t', 'safe_ptr_mrpt_opengl_Scene_t', 'safe_ptr_mrpt_rtti_TRuntimeClassId_t', 'serialization', 'sign', 'signWithZero', 'slam', 'square', 'system', 'tfest', 'toNativeEndianness', 'to_string', 'topography', 'typemeta', 'u8tof', 'uint_select_by_bytecount_1_t', 'uint_select_by_bytecount_2_t', 'uint_select_by_bytecount_3_t', 'uint_select_by_bytecount_4_t', 'uint_select_by_bytecount_8_t', 'vision']

I do see other modules that I recognize from docs (e.g. poses, slam, etc..), but no ros1bridge. Am I missing something or has this binding been omitted?

[jlblancoc]

Oh my! You are right, it was totally left out (!).

Following up in #1276.