Couldn't add children widget to box when rendering widgets

Hi,

I don’t know if there is a bug in ipywidgets or if there’s an opportunity to refactor IPythonKernel. I’d appreciate your comments.

I recently created a kernel that inherits directly from IPythonKernel: class MyKernel(IPythonKernel) This MyKernel class is a very thin layer over the IPythonKernel.

On this kernel, if the user tries to display a Widget in MyKernel, they’ll get a Javascript error that I am having a very hard time debugging. Message from browser console below. Notice that the widget tabs omit the content of the widget children:

When i run the same piece of code that renders the same widget on the real IPythonKernel, it looks like this, with children displaying correctly:

Any help would be appreciated!

Thanks!

Javascript error message:

Uncaught (in promise) WrappedError {stack: "Error: Couldn't add child view to box↵    at new E…in.js?v=40e10638fcf65fc1c057bff31d165e9d:12785:33", message: "Couldn't add child view to box", error_stack: Array[4]}error_stack: Array[4]0: TypeError: require is not a function
    at http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:12740:17
    at Object.load_class (http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:12736:16)
    at http://localhost:8888/nbextensions/widgets/widgets/js/manager.js?v=20151103005149:74:261: Error: Couldn't create a view for model id '5ce5e524d89f44fd84f229604853b122'
    at new Error (native)
    at Error.WrappedError (http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:12706:25)
    at http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:12785:33message: "Couldn't create a view for model id '5ce5e524d89f44fd84f229604853b122'"stack: (...)get stack: ()set stack: ()__proto__: DefineError.bh2: Error: Couldn't create child view
    at new Error (native)
    at Error.WrappedError (http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:12706:25)
    at http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:12785:33message: "Couldn't create child view"stack: (...)get stack: ()set stack: ()__proto__: DefineError.bh3: Error: Couldn't add child view to box
    at new Error (native)
    at Error.WrappedError (http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:12706:25)
    at http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:12785:33length: 4__proto__: Array[0]message: "Couldn't add child view to box"stack: "Error: Couldn't add child view to box↵    at new Error (native)↵    at Error.WrappedError (http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:12706:25)↵    at http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:12785:33"__proto__: Object

ping @ellisonbg

[aggFTW]

Visitors from the future:

My issue was I had installed ipywidgets via pip with a conda installation and there was indeed a version mismatch between the conda and pip ipywidget installation.

When I resolved the inconsistency, issue went away.

Thanks for the help everyone!

[aggFTW]

So I’ve been looking at this all night and cannot figure out what’s going on…

Both kernels are using the same Python version, running on the same kernel. Furthermore, I also just experienced this in the ipython kernel itself. It’s weird because I have another notebook where it works.

I installed ipywidgets from master and cleared the browser. Now, I get this error message on first execution:

0: Error: Class ipython.widget not found in registry at http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:12751:28 at O (eval at <anonymous> (http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:89:4231), <anonymous>:8:15049) at new V (eval at <anonymous> (http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:89:4231), <anonymous>:8:16254) at Object.load_class (http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:12736:16) at CommManager.comm_open (http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:21802:37) at x.isFunction.i (http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:89:5488) at Kernel._handle_iopub_message (http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:23101:20) at Kernel._finish_ws_message (http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:22936:29) at http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:22926:44 at P (eval at <anonymous> (http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:89:4231), <anonymous>:8:14792)
1: Error: Could not open comm at new Error (native) at Error.WrappedError (http://localhost:8888/static/notebook/js/main.min.js?v=40e10638fcf65fc1c057bff31d165e9d:12706:25) at...

As far as I know I only have Anaconda’s Python 2.7 (Python 2.7.10 |Anaconda 2.3.0 (x86_64)) and one version of ipywidgets installed (‘4.2.0.dev’).

I did some searches and found this: https://github.com/ipython/ipython/pull/6493 Maybe @SylvainCorlay would know? 😃

@ellisonbg How can I verify if ipywidgets is installed propertly (with the JS) in both? I didn’t quite get that question.

Thanks in advance!