Adding support for python bindings

[patricknaughton01]

Can build shared library for python bindings by specifying
-DBUILD_PYTHON=ON when calling cmake. This requires pybind11
to be cloned into build's parent directory. The python bindings
expose a very minimal interface: it allows construction of a
GraspDetector and calling detectGrasps which accepts a
previously instantiated GraspDetector and a point cloud as a
numpy array (of shape (n, 3)). This function returns a numpy
array of shape (number of grasps, 14) where the columns specify
the position, orientation (rotation matrix in row-major order), the width
of the gripper, and the score of the grasp.

[patricknaughton01]

One remark is that it seems like the Eigen predictor segfaults if the weights file is not found.

[pvmilk]

I am just another user of the repo that looking into these features recently.

Wondering what is the difference between this implementation and the one in https://github.com/atenpas/gpd/blob/master/src/detect_grasps_python.cpp.

P.S. I am not familiar with cpp2python binding at all, so please excuse me for some silly questions.

[pvmilk]

I guess this stackoverflow is the answer to
https://github.com/atenpas/gpd/blob/master/src/detect_grasps_python.cpp.

[patricknaughton01]

I was unaware actually of that method you linked. I just used pybind because I've used it before and it works nicely with numpy arrays. I haven't tried it, but do you know if the cdll/the existing python code will let you pass in a numpy array?

[pvmilk]

I am testing it at the moment. Still cannot get it compiled. But will report back if I got anything from it.
But looking from here, maybe it is ok.

[pvmilk]

FYI, the provide binding detect_grasps_python.cpp works with some modification, and numpy array can be pass through that ctypes python interface. Can provide the patch if anyone needed it (Update as of July 2023).

[tycoer]

Can build shared library for python bindings by specifying -DBUILD_PYTHON=ON when calling cmake. This requires pybind11 to be cloned into build's parent directory. The python bindings expose a very minimal interface: it allows construction of a GraspDetector and calling detectGrasps which accepts a previously instantiated GraspDetector and a point cloud as a numpy array (of shape (n, 3)). This function returns a numpy array of shape (number of grasps, 14) where the columns specify the position, orientation (rotation matrix in row-major order), the width of the gripper, and the score of the grasp.

Hi, after I install your branch, I use the commend 'python3 test.py', the python shows "No module named gpd_python".

I use the following commend when I install your branch:
mkdir build && cd build
cmake -DBUILD_PYTHON=ON ..
make -j8
sudo make install

I already installed pybind11 under the parent dir, and no error occurred during compiling.

However, "No module named gpd_python".

Maybe there should be a "setup.py" file that I can "python setup.py develop" to install "gpd_python"?

or

Any step I wrongly ran caused "No module named gpd_python"

[patricknaughton01]

The library might be inside the build directory in which case you might be able to solve via any one of the following:

• Move either test.py or the built shared library into the same directory.
• Add the build directory to the python path (sys.path.append("build/"))
• Change the import to from build import gpd_python as gpd

Let me know if these don't work. Thanks.

[tycoer]

The library might be inside the build directory in which case you might be able to solve via any one of the following:

• Move either test.py or the built shared library into the same directory.
• Add the build directory to the python path (sys.path.append("build/"))
• Change the import to from build import gpd_python as gpd

Let me know if these don't work. Thanks.

It works, Thanks!!

[anmakon]

FYI, the provide binding detect_grasps_python.cpp works with some modification, and numpy array can be pass through that ctypes python interface. Can provide the patch if anyone needed it.

Hi @pvmilk,
do you by any chance still have that patch? I'm looking into using GPD in python with an indexed pointcloud, which I think should be possible with the function calcGraspDescriptorsAtIndices, but I can't quite get it to compile yet.

[pvmilk]

@anmakon Sorry for the late response. I searched through my system and cannot find the patch anymore. Sorry to give a false expectation.