Codefolding

This extension adds codefolding functionality from CodeMirror to a codecell.

After clicking on the gutter (left margin of codecell) or typing Alt+F, the code gets folded. See the examples below. The folding status is saved in the cell metadata of the notebook, so reloading of a notebook will restore the folding view.

Supported modes:

Three different folding modes are supported:

Indent Folding

Python-style code folding, detetects indented code.

The unfolded code above can be folded like this:

or this:

Bracket Folding

Other languages like Javascript use brackets to designate code blocks. Codefolding is supported for Javascript in using the %%javsscript magic in a codecell.

Firstline Comment Folding

Allows collapsing of Python code cells to a single comment line. This is useful for long codecells. The algorithm simply looks for a comment in the first line and allows folding in the rest of the cell.

The code above can be folded like this:

Installation

Copy the codefolding directory to a new /nbextensions/usability/codefolding directory of your local .ipython directory. Then load the extension from within the IPyton notebook:

%%javascript
IPython.load_extensions('usability/codefolding/codefolding.js');

Alternatively, you can add the load command to your custom.js. Take a look at the general installation instructions in the Wiki if you are unsure how to proceed.

Internals

You need the current master branch from Codemirror in order to get codefolding to work. This is still very much work-in-progress.

The folding information is saved in the metadata of each codecell. The number of the folding start line (beginning with 0) is stored in an array:

cell.metadata.code_folding = [ 3, 20, 33 ]

When reloading the IPython notebook, the folding status is restored.