Kernel ext, start of JS

pages/4-ways-to-extend-jupyter-notebook/index.md

@@ -1,7 +1,7 @@
 Title: Four Ways to Extend Jupyter Notebook
 Date: 2015-07-07
 
-[Jupyter Notebook](https://try.jupyter.org/) (née [IPython Notebook](http://ipython.org)) is a web-based notebook environment for interactive computing. In addition to supporting the execution of user-defined code in notebook documents, Jupyter Notebook has a variety of code plug-in points which one can use to extend the capabilities of the tool itself. In this post, I'll touch on four of these extension mechanisms, some better known than others, and finish off with an example of how to package and distribute a set of cooperating extensions.
+[Jupyter Notebook](https://try.jupyter.org/) (née [IPython Notebook](http://ipython.org)) is a web-based environment for interactive computing in notebook documents. In addition to supporting the execution of user-defined code, Jupyter Notebook has a variety of plug-in points which one can use to extend the capabilities of the authoring environment itself. In this post, I'll touch on four of these extension mechanisms, some better known than others, and finish off with an example of how to package and distribute a set of cooperating extensions.
 
 ## 1. Kernels
 
@@ -21,14 +21,64 @@ Creating new kernels can be as simple as implementing [a Python `IPython.kernel.
 
 ## 2. Kernel Extensions
 
-%load_ext
-%install_ext
-%reload_ext
-%unload_ext
+[Kernel extensions](http://ipython.org/ipython-doc/dev/config/extensions/index.html) are Python modules that can modify the interactive shell environment within an IPython kernel. Such extensions can register [magics](https://ipython.org/ipython-doc/3/interactive/tutorial.html#magic-functions), define variables, and generally modify the user namespace to provide new features for use within code cells. Kernel extensions are not exclusive to the Jupyter Notebook frontend, but many [community contributed extensions](https://github.com/ipython/ipython/wiki/Extensions-Index) do target its browser-powered display system in particular.
 
-## 3. Notebook Frontend Extensions
+The IPython kernel ships with four magics that enable the management of extensions from within notebooks (or other Jupyter interfaces).
+
+1. `%install_ext <URL|path>` installs a Python module as an extension 
+2. `%load_ext <name>` loads the extension module and invokes its load function
+3. `%reload_ext <name>` invokes the extension module unload function, reloads the extension module itself, and then invokes its load function 
+4. `%unload_ext <name>` invokes the extension module unload function and drops the module reference
+
+Likewise, the Jupyter configuration system exposes the `InteractiveShellApp.extensions` trait which loads a list of Python modules for every new IPython kernel launched.
+
+```
+c.InteractiveShellApp.extensions = [
+    'mypackage.myextension'
+]
+```
+
+Writing a Python module that can serve as a kernel extension requires implementing a `load_ipython_extension` function and optionally implementing `unload_ipython_extension`. Both functions receive an [`InteractiveShell`]() instance as their one and only parameter. The loading function typically uses methods on the instance to add features while the unload function cleans them up.
+
+## 3. Notebook Extensions
+
+Jupyter Notebook extensions (*nbextensions*) are JavaScript modules that can load on most major web pages comprising the Notebook frontend. Once loaded, they have access to the complete page DOM and frontend Jupyter JavaScript API with which to modify the notebook, dashboard, editor, etc. user experience. As their name suggests, these extensions are exclusive to the Notebook frontend for Jupyter and [typically add features to the notebook authoring portion of the user interface.](https://github.com/ipython-contrib/IPython-notebook-extensions/wiki/Home_3x)
+
+Install.
+
+
+```
+import IPython
+IPython.html.nbextensions.install_nbextension('https://rawgithub.com/minrk/ipython_extensions/master/nbextensions/gist.js', user=True)
+```
+
+Load one-off
+
+```
+%%javascript
+IPython.load_extensions('gist');
+```
+
+Install.
+
+```
+from IPython.html.services.config import ConfigManager
+ip = get_ipython()
+cm = ConfigManager(parent=ip, profile_dir=ip.profile_dir.location)
+cm.update('notebook', {"load_extensions": {"gist": True}})
+```
+
+Uninstall.
+
+```
+from IPython.html.services.config import ConfigManager
+ip = get_ipython()
+cm = ConfigManager(parent=ip, profile_dir=ip.profile_dir.location)
+cm.update('notebook', {"load_extensions": {"gist": None}})
+```
+
+Writing one: AMD, requirejs, DOM manipulation, Jupyter JS API
 
-JavaScript requirejs, AMD
 
 ## 4. Notebook Server Extensions