Altair: Cross incompatibility with altair and nteract vs classic notebook

[josephofiowa]

Altair does not work in the classic Jupyter Notebook after successfully using it in an nteract web notebook.

Altair works in nteract without a user needing to run alt.renderers.enable('notebook'). e.g. this notebook works https://github.com/nteract/nteract/blob/master/applications/desktop/example-notebooks/altair.ipynb when launched with jupyter nteract.

When using Altair without nteract, a user must run alt.renderers.enable('notebook'). However, this returns the below error. As per the Altair troubleshooting guide, Altair believes Vega is not installed. Even upon verifying successful Altair + Vega installation (as per the installation guide ), the error persists. conda list verified Vega is installed. I am using Jupyter Notebook 5.6.0.

Do you know what may be causing this?
cc @rgbkrk

---------------------------------------------------------------------------
NoSuchEntryPoint                          Traceback (most recent call last)
~/anaconda3/lib/python3.6/site-packages/altair/utils/plugin_registry.py in _enable(self, name, **options)
    133             try:
--> 134                 ep = entrypoints.get_single(self.entry_point_group, name)
    135             except entrypoints.NoSuchEntryPoint:

~/anaconda3/lib/python3.6/site-packages/entrypoints.py in get_single(group, name, path)
    185 
--> 186     raise NoSuchEntryPoint(group, name)
    187 

NoSuchEntryPoint: No 'notebook' entry point found in group 'altair.vegalite.v2.renderer'

During handling of the above exception, another exception occurred:

ValueError                                Traceback (most recent call last)
<ipython-input-4-025c0cf17452> in <module>()
----> 1 alt.renderers.enable('notebook')

~/anaconda3/lib/python3.6/site-packages/altair/utils/plugin_registry.py in enable(self, name, **options)
    169         if name is None:
    170             name = self.active
--> 171         return PluginEnabler(self, name, **options)
    172 
    173 

~/anaconda3/lib/python3.6/site-packages/altair/utils/plugin_registry.py in __init__(self, registry, name, **options)
     23         self.options = options
     24         self.original_state = registry._get_state()
---> 25         self.registry._enable(name, **options)
     26 
     27     def __enter__(self):

~/anaconda3/lib/python3.6/site-packages/altair/utils/plugin_registry.py in _enable(self, name, **options)
    135             except entrypoints.NoSuchEntryPoint:
    136                 if name in self.entrypoint_err_messages:
--> 137                     raise ValueError(self.entrypoint_err_messages[name])
    138                 else:
    139                     raise

ValueError: 
To use the 'notebook' renderer, you must install the vega package
and the associated Jupyter extension.
See https://altair-viz.github.io/getting_started/installation.html
for more information.

[jakevdp]

You need to pip install vega==1.3. vega version 2.0 does not work with the current release of Altair. See #1114

[josephofiowa]

@jakevdp Thank you. Success.

(FYI to others that may find themselves here -- alt.renderers.enable('notebook') is not still required in nteract for successful load)

[jakevdp]

alt.renderers.enable('notebook') is not still required in nteract for successful load)

The notebook renderer was never required for nteract. Where did you hear that? I'd like to correct that information if it's out there somewhere.

[josephofiowa]

This is the result of my misunderstanding rather than explicit instruction.

Note this notebook, which is meant to be loaded in nteract, displays

If you see this message, it means the renderer has not been properly enabled
for the frontend that you are using. For more information, see
https://altair-viz.github.io/user_guide/troubleshooting.html

when rendered on GitHub.

[jakevdp]

I see. Maybe it would be useful to add some nteract-specific information to https://altair-viz.github.io/user_guide/troubleshooting.html and to https://altair-viz.github.io/getting_started/installation.html ?

I've never used nteract, so I don't have the background to be able to add relevant details. A doc contribution would be welcome – the source is here: https://github.com/altair-viz/altair/blob/master/doc/getting_started/installation.rst

[jakevdp]

Also, the reason github shows that message rather than a plot is because it scrubs all javascript output. In jupyter notebook and jupyterlab, the respective vega extension is set up to cache a png preview of every rendered plot as a fallback for github, nbviewer, and other non-js-enabled notebook views.

Maybe nteract could add that feature as well to avoid this confusion?

[rgbkrk]

In jupyter notebook and jupyterlab, the respective vega extension is set up to cache a png preview of every rendered plot as a fallback for github, nbviewer, and other non-js-enabled notebook views.

Maybe nteract could add that feature as well to avoid this confusion?

I'll do some thinking on that. We've largely kept rendering pure, assuming that we'd only report what kernels provide. 🤔 I could see a way of us handling it in the future.

When the plots are interactive, do you store the changed result?

[jakevdp]

When the plots are interactive, do you store the changed result?

No, the PNG is rendered at the time the plot is displayed. You can see the source here: https://github.com/vega/ipyvega/blob/master/src/index.ts#L22-L35