How to get the current notebook panel?

JupyterLab extensions
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1

Hi,

I am trying to make an extension that creates and opens up an .ipynb file automatically. I need to get the current notebook panel after opening up the file. I have found that I can use INotebookTracker to get the current notebook

function activate(app:JupyterFrontEnd, notebookTracker: INotebookTracker) {
    const nbPanel1: any = notebookTracker;
    console.log(nbPanel1)
}

I can see from the console.log that nbPanel1 contains currentWidget, which indeed points to the current NotebookPanel which contains my current file (“renamed.ipynb”) opened.

image
image898Ă—1100 202 KB

However, when I try to extract just the widget i.e. NotebookPanel, which from the documentation here it seems I should be able to do:

function activate(app:JupyterFrontEnd, notebookTracker: INotebookTracker) {
    const nbPanel1: any = notebookTracker;
    console.log(nbPanel1);
    const nbPanel2: any = notebookTracker.currentWidget;
    console.log(nbPanel2);
}

From the console log nbPanel2 does not return the NotebookPanel that I saw in nbPanel1's currentWidget value as expected, instead it returns null.

Why is it not able to return the currentWidget object i.e. the NotebookPanel that I saw in nbPanel1?

Is there a better way to extract the current NotebookPanel?

Thank you for your help!

2

Very close: further down that API page, it hints at how one might listen for when the widget changes:

function activate(app:JupyterFrontEnd, notebookTracker: INotebookTracker) {
  notebookTracker.currentChanged.connect((tracker, panel) => {
    console.log(panel);
  });
}
  • the type on that panel, like currentWidget might still be null (e.g. when all of the notebooks have closed).
  • this is a signal
    • these are worth understanding, as most of the “good stuff” in the core functionality can be efficiently observed through this means
3

Awesome, this works perfectly. Thanks for the answer and explanations! It is very much appreciated :blush:

4

Hello, I have tried using this code snippet however I get “TypeError: can’t access property “currentChanged”, notebookTracker is undefined”.

Am I missing something else?

function activate(
    app: JupyterFrontEnd,
    mainMenu: IMainMenu,
    settings: ISettingRegistry,
    panel: NotebookPanel,
    notebookTracker: INotebookTracker): void {
    console.log('JupyterLab extension myextension is activated!');

    notebookTracker.currentChanged.connect((tracker, panel) => {
        console.log(`Tracker => ${panel}`)
    })
}

Screen Shot 2022-09-23 at 12.24.18
Screen Shot 2022-09-23 at 12.24.181256Ă—238 56.8 KB

Thank you very much in advance for the pointers and clarifications

5

Hello again, I just found the issue, it was my bad that I didn’t keep the components passed to the active function in the same order I have them in my requires. Once I fixed that, the notebookTracker had information.

The answer to a similar question gave me the pointer I needed: jupyter - How do you get the currently active notebook name in JupyterLab? - Stack Overflow

Thank you very much though I know someone will answer eventually :smile: