Notebook — JupyterLab 4.4.1 documentation (original) (raw)

Background#

A JupyterLab architecture walkthrough from June 16, 2016, provides an overview of the notebook architecture.

The most complicated plugin included in the JupyterLab applicationis the Notebook plugin.

TheNotebookWidgetFactoryconstructs a newNotebookPanelfrom a model and populates the toolbar with default widgets.

Structure of the Notebook plugin#

The Notebook plugin provides a model and widgets for dealing with notebook files.

Model#

TheNotebookModelcontains an observable list of cells.

A cell modelcan be:

A code cell contains a list of output models. The list of cells and the list of outputs can be observed for changes.

Cell operations#

The NotebookModel cell list supports single-step operations such as moving, adding, or deleting cells. Compound cell list operations, such as undo/redo, are also supported by the NotebookModel. Right now, undo/redo is only supported on cells and is not supported on notebook attributes, such as notebook metadata. Currently, undo/redo for individual cell input content is supported by the CodeMirror editor’s undo feature. (Note: CodeMirror editor’s undo does not cover cell metadata changes.)

Metadata#

The notebook model and the cell model (i.e. notebook cells) support getting and setting metadata through method getMetadata, setMetadataand deleteMetadata (see NotebookModeland cell model). You can listen for changes in the metadata through the sharedModel.metadataChanged attribute (see cell shared modeland notebook shared model).

Notebook widget#

After the NotebookModel is created, the NotebookWidgetFactory constructs a new NotebookPanel from the model. The NotebookPanel widget is added to the DockPanel. The NotebookPanel contains:

The NotebookPanel also adds completion logic.

The Notebook toolbar maintains a list of widgets to add to the toolbar. The Notebook widget contains the rendering of the notebook and handles most of the interaction logic with the notebook itself (such as keeping track of interactions such as selected and active cells and also the current edit/command mode).

The NotebookModel cell list provides ways to do fine-grained changes to the cell list.

Higher level actions using NotebookActions#

Higher-level actions are contained in theNotebookActionsnamespace, which has functions, when given a notebook widget, to run a cell and select the next cell, merge or split cells at the cursor, delete selected cells, etc.

Widget hierarchy#

A Notebook widget contains a list of cell widgets, corresponding to the cell models in its cell list.

ACodeCellalso contains anOutputArea. An OutputArea is responsible for rendering the outputs in theOutputAreaModellist. An OutputArea uses a notebook-specificRenderMimeRegistryobject to render display_data output messages.

The Notebook widget is represented in the DOM with a <div> element with CSS classes jp-Notebook and jp-NotebookPanel-notebook. It contains a sequence of cells widgets.

Note

The default nbconvert template for the HTML exporter produces the same DOM as the JupyterLab notebook, allowing for the JupyterLab CSS to be used directly. In JupyterLab, input areas are rendered with the CodeMirror, with a custom theme making use of the CSS variables of JupyterLab. In the case of nbconvert, code cells are rendered using the Pygments Python library, which produces static HTML with syntax highlighting. Thejupyterlab_pygmentsPygments theme mimics the default CodeMirror theme of JupyterLab.

Note

The SVG figures presenting the DOM structures of the different cell types were produced with Draw.io, and contain the metadata allowing them to be directly opened and edited with Draw.io.

Rendering output messages#

A Rendermime plugin provides a pluggable system for rendering output messages. Default renderers are provided for markdown, html, images, text, etc. Extensions can register renderers to be used across the entire application by registering a handler and mimetype in the rendermime registry. When a notebook is created, it copies the global Rendermime singleton so that notebook-specific renderers can be added. The ipywidgets widget manager is an example of an extension that adds a notebook-specific renderer, since rendering a widget depends on notebook-specific widget state.

Keyboard interaction model#

Multiple elements can receive focus in the Notebook: - the main toolbar, - cells, - cell components (editor, toolbar, outputs).

When the focus is outside of the cell input editor, the Notebook switches to so-called “command” mode. In the command mode additional keyboard shortcuts are accessible to the user, enabling quick access to cell- and notebook-specific actions. These shortcuts are only active when the notebook is in command mode and the active element is non-editable, as signalled by absence of .jp-mod-readWrite class on the notebook node. This class is set if the active element is editable as ascertained by matching to the :read-write pseudo-selector, and accounts for any elements nested in the open shadow DOM, but not for the closed shadow DOM nor non-editable elements with custom key event handlers (such as<div contenteditable="false" onkeydown="alert()" tabindex="0"></div>). If your output widget (for example created with IPython.display.HTML, or created by your MIME renderer on cell output in a notebook or console) uses closed shadow DOM or non-editable elements with custom key event handlers, you may wish to set lm-suppress-shortcuts data attribute on the host element to prevent side-effects from the command-mode actions, e.g:

Click on me and press "A" with and without "lm-suppress-shortcuts"

How to extend the Notebook plugin#

We’ll walk through two notebook extensions:

Adding a button to the toolbar#

Since JupyterLab 3.2, adding toolbar item can be done using a Toolbar Registry and settings. In particular for the notebook, if the button is linked to a new command, you can add a button in the toolbar using the following JSON snippet in your extension settings file:

"jupyter.lab.toolbars": { "Notebook": [ // Widget factory name for which you want to add a toolbar item. // Item with default button widget triggering a command { "name": "run", "command": "runmenu:run" } ] }

You may add a rank attribute to modify the item position (the default value is 50).

The ipywidgets third party-extension#

This discussion will be a bit confusing since we’ve been using the term_widget_ to refer to lumino widgets. In the discussion below,Jupyter interactive widgets will be referred to as ipywidgets. There is no intrinsic relation between lumino widgets and Jupyter interactive widgets.

The ipywidgets extension registers a factory for a notebook _widget_extension using the Document Registry. The createNew() function is called with a NotebookPanel andDocumentContext. The plugin then creates a ipywidget manager (which uses the context to interact the kernel and kernel’s comm manager). The plugin then registers an ipywidget renderer with the notebook instance’s rendermime (which is specific to that particular notebook).

When an ipywidget model is created in the kernel, a comm message is sent to the browser and handled by the ipywidget manager to create a browser-side ipywidget model. When the model is displayed in the kernel, a display_data output is sent to the browser with the ipywidget model id. The renderer registered in that notebook’s rendermime is asked to render the output. The renderer asks the ipywidget manager instance to render the corresponding model, which returns a JavaScript promise. The renderer creates a container lumino widget which it hands back synchronously to the OutputArea, and then fills the container with the rendered ipywidget when the promise resolves.