DirectionalLight on Google Colab

[francesco-ballarin]

Hi,
I am trying to use pythreejs on Google Colab, and I am seeing a failure related to DirectionalLight.

A minimal notebook to reproduce has the following content:

# Cell 1: installation
!pip install pythreejs

# Cell 2: allow custom widgets
from google.colab import output
output.enable_custom_widget_manager()

# Cell 3: import pythreejs
from pythreejs import *

# Cell 4: create a simple widget
BoxGeometry(
    width=5,
    height=10,
    depth=15,
    widthSegments=5,
    heightSegments=10,
    depthSegments=15)

# Cell 5: create a light object
DirectionalLight(color='white', position=[3, 5, 1], intensity=0.5)

Cell 4 runs correctly, the box shows up and the user can interact with it.
Cell 5 runs, a black background gets rendered, but immediately below the black widget there are several instances of

---------------------------------------------------------------------------
TraitError                                Traceback (most recent call last)
[/usr/local/lib/python3.7/dist-packages/ipywidgets/widgets/widget.py](https://localhost:8080/#) in _handle_msg(self, msg)
    754                 if 'buffer_paths' in data:
    755                     _put_buffers(state, data['buffer_paths'], msg['buffers'])
--> 756                 self.set_state(state)
    757 
    758         # Handle a state request.

5 frames
[/usr/local/lib/python3.7/dist-packages/ipywidgets/widgets/widget.py](https://localhost:8080/#) in set_state(self, sync_data)
    623                     from_json = self.trait_metadata(name, 'from_json',
    624                                                     self._trait_from_json)
--> 625                     self.set_trait(name, from_json(sync_data[name], self))
    626 
    627     def send(self, content, buffers=None):

[/usr/local/lib/python3.7/dist-packages/traitlets/traitlets.py](https://localhost:8080/#) in set_trait(self, name, value)
   1436                                 (cls.__name__, name))
   1437         else:
-> 1438             getattr(cls, name).set(self, value)
   1439 
   1440     @classmethod

[/usr/local/lib/python3.7/dist-packages/traitlets/traitlets.py](https://localhost:8080/#) in set(self, obj, value)
    578 
    579     def set(self, obj, value):
--> 580         new_value = self._validate(obj, value)
    581         try:
    582             old_value = obj._trait_values[self.name]

[/usr/local/lib/python3.7/dist-packages/traitlets/traitlets.py](https://localhost:8080/#) in _validate(self, obj, value)
    610             return value
    611         if hasattr(self, 'validate'):
--> 612             value = self.validate(obj, value)
    613         if obj._cross_validation_lock is False:
    614             value = self._cross_validate(obj, value)

[/usr/local/lib/python3.7/dist-packages/traitlets/traitlets.py](https://localhost:8080/#) in validate(self, obj, value)
   1985                 except TraitError:
   1986                     continue
-> 1987         self.error(obj, value)
   1988 
   1989     def __or__(self, other):

[/usr/local/lib/python3.7/dist-packages/traitlets/traitlets.py](https://localhost:8080/#) in error(self, obj, value, error, info)
    690                     e = "The '%s' trait expected %s, not %s." % (
    691                         self.name, self.info(), describe("the", value))
--> 692                 raise TraitError(e)
    693 
    694     def get_metadata(self, key, default=None):

TraitError: The 'target' trait of a DirectionalLight instance expected an Uninitialized or an Object3D, not the str 'IPY_MODEL_[object Object]'.

I suspect that some of pythreejs dependencies already pre-installed on Colab are quite old, and by running pip install --upgrade on the right dependency the error would disappear. Unfortunately, I can't pinpoint which dependency I should upgrade. Can you help me with that?

The only dependency I am confident one must not upgrade is ipywidgets: it seems that doing so would make Cell 2 ineffective, and Cell 2 is fundamental for the widget in Cell 4 to correctly show up.

The same notebook, and much more complicated ones, run correctly on my local jupyter lab installation.

[cmaurini]

Hi, as @francesco-ballarin, I have issue when trying to use pythreejs in colab as pyvista backend. The issue is probably related to the one reported above. Do you have any update?

[hakonanes]

I can reproduce the above error on my local JupyterLab installation on Ubuntu 22.04, no connection to Google Colab. I initially encountered this error using pythreejs via PyVista.

Versions (not sure which ones are most important):

• python 3.10.8
• pythreejs 2.4.1
• ipywidgets 7.7.0 (not newer to avoid pyvista (pythreejs or ipygany backend) incompatible with ipywidgets>7.7.2. pyvista/pyvista#3274)
• jupyterlab 3.5.1
• traitlets 5.7.0

[francesco-ballarin]

Thanks @hakonanes , so it seems that the issue may affect jupyterlab installations as well. After 3 months, it would be nice to have a comment or suggestion from pythreejs develoeprs.

[zou000]

The problem is not specific to DirectionalLight, SpotLight has the same problem.

[kazumamatata]

I also got this error on my local macOS, after upgrading my packages.

Now, I could find a temporary fix.
When downgrading traitlets from latest 5.8.0 to 4.3.3, the error disappeared.

For that I wrote the environment.yml file and created a conda environment:

conda env create --file environment.yml

environment.yml:

name: pjs
channels:
- conda-forge
dependencies:             
- python=3.9
- jupyterlab
- pythreejs
- pyvista
- traitlets=4.3.3

By removing the last line, the above mentioned error appears again.

P.S. Strangely pythreejs worked with traitlets v5.7.1 before, so I am wondering why this problem occurs

[francesco-ballarin]

Thanks @kazumamatata for the report and the workaround on macOS.

In terms of the original bug report (on Colab), I want to point out for pythreejs developers that

1. neither v5.7.1 nor v5.8 of traitlets were released at the time of the original bug report (the latest released version in September 2022 was v5.4.0)
2. upgrading/downgrading traitlets does not seem feasible on Colab, since it requires to force a kernel restart (due to being imported on startup, I guess)

[vidartf]

I did a bit of troubleshooting on this, and noted the following:

• This happens also if I simply install pythreejs with recent version of everything. No other packages / envs are important in order to repro the current error.
• I install jupyterlab-kernelspy to inspect the comm messages, and found this error occurs when the default "target" for a DirectionalLight is created from the kernel side:

   Exception opening comm with target: jupyter.widget
   Traceback (most recent call last):
   File "<env root>lib\site-packages\comm\base_comm.py", line 237, in comm_open f(comm, msg)
   File "<env root>lib\site-packages\ipywidgets\widgets\widget.py", line 427, in handle_comm_opened widget = widget_class(comm=comm)
   File "<env root>lib\site-packages\pythreejs\core\Object3D_autogen.py", line 26, in __init__ super(Object3D, self).__init__(**kwargs)
   File "<env root>lib\site-packages\pythreejs\_base\Three.py", line 17, in __init__ super(ThreeWidget, self).__init__(**kwargs)
   File "<env root>lib\site-packages\ipywidgets\widgets\widget.py", line 502, in __init__ super().__init__(**kwargs)
   File "<env root>lib\site-packages\traitlets\traitlets.py", line 1346, in __init__ setattr(self, key, value)
   File "<env root>lib\site-packages\traitlets\traitlets.py", line 732, in __set__ self.set(obj, value)
   File "<env root>lib\site-packages\traitlets\traitlets.py", line 706, in set new_value = self._validate(obj, value)
   File "<env root>lib\site-packages\traitlets\traitlets.py", line 738, in _validate value = self.validate(obj, value)
   File "<env root>lib\site-packages\traitlets\traitlets.py", line 2150, in validate self.error(obj, value)
   File "<env root>lib\site-packages\traitlets\traitlets.py", line 844, in error
   raise TraitError(e) traitlets.traitlets.TraitError: The 'comm' trait of an Object3D instance expected a Comm or None, not the BaseComm at '0x13ea2217df0'.

• The creation of the DirectionalLight fails after that, since it is referencing a widget that failed to create.
• I note that the error during the client side initiated comm_open message is not shown in the log viewer in lab. This should ideally be added in Lab.
• The comm issue is likely to be an ipywidgets bug (cc @jasongrout for visibility)

[vidartf]

It might also be an issue in the new comm package (cc @martinRenou ).

[vidartf]

Ah, I had ipykernel 6.19.4, which has been pulled from PyPI, but is still up on conda-forge... Downgrading to ipykernel 6.16.2 seems to have fixed the issue for me locally. I'm guessing that downgrading to traitlets 4 indirectly fixed it by constraining which version of ipykernel that you could have, since it currently depends on traitlets>=5.4.0. If someone can repro this error with ipykernel<=6.16.2 , please add some detailed repro steps, and I can look again.

[francesco-ballarin]

If someone can repro this error with ipykernel<=6.16.2

Colab is quite a lot behind current releases, and therefore definitely satisfies that condition. See https://github.com/googlecolab/backend-info/blob/2cec3e7ca1ae121133d9f8ee350e2aebf4518293/pip-freeze.txt#L163

[vidartf]

To troubleshoot colab issues, I suggest you reach out to colab :)

[francesco-ballarin]

Done that, googlecolab/colabtools#3159 ;)

[francesco-ballarin]

My main motivation was using pythreejs within pyvista. Since the pythreejs backend was removed from pyvista in pyvista/pyvista#4687, I don't have any further interest in this, hence I am closing this. Feel free to reopen if someone else is interested in this for pythreejs on its own, rather than within pyvista.