IPython notebook extension with some debugging output

python-markdown.js

// Allow Python-code in markdown cells
// Encapsulate using {{...}}
// - You can also return html or markdown from your Python code
// - You can embed images, however they will be sanitized on reload.
"use strict";

var pymd_extension = (function() {
    "use strict";
    var security = IPython.security;
    var _on_reload = true; /* make sure cells with variables render on reload */
    
    var execute_python = function(cell,text) {
        /* always clear stored variables if notebook is dirty */
        if (IPython.notebook.dirty == true) cell.metadata.variables = {}; 
    
        // search for code in double curly braces: {{}}
        text = text.replace(/{{(.*?)}}/g, function(match,tag,cha) {
            if (tag == "") return match;

            var code = tag;
            var id = 'python_'+cell.cell_id+'_'+cha; /* create an individual ID */
            var thiscell = cell;
            var thismatch = tag;
            
            /* there a two possible options:
               a) notebook dirty or variable not stored in metadata: evaluate variable
               b) notebook clean and variable stored in metadata: only display 
            */
            var val = cell.metadata.variables;
            if (val == undefined) cell.metadata.variables = {}; 
            val = cell.metadata.variables[thismatch];
            if (IPython.notebook.dirty == true || val == undefined) {
                console.log("PyMD: execute")   
                cell.metadata.variables[thismatch] = {}; 
                cell.callback = function (out_data)
                        {
                        var has_math = false;
                        var ul = out_data.content.data;
                        //console.log("ul:",ul);
                        if (ul != undefined) {
                            if ( ul['text/latex'] != undefined) {
                                var html = ul['text/latex'];
                                has_math = true;
                            } else if ( ul['image/svg+xml'] != undefined) {
                                var svg =  ul['image/svg+xml'];
                                /* embed SVG in an <img> tag, still get eaten by sanitizer... */
                                svg = btoa(svg); 
                                var html = '<img src="data:image/svg+xml;base64,'+ svg + '"/>';
                            } else if ( ul['image/jpeg'] != undefined) {
                                var jpeg =  ul['image/jpeg'];
                                var html = '<img src="data:image/jpeg;base64,'+ jpeg + '"/>';
                            } else if ( ul['image/png'] != undefined) {
                                var png =  ul['image/png'];
                                var html = '<img src="data:image/png;base64,'+ png + '"/>';
                            } else if ( ul['text/html'] != undefined) {
                               var html = ul['text/html'];
                            } else {
                                var result = (ul['text/plain']);
                                html = marked(result);
                                var t = html.match(/<p>(.*?)<\/p>/)[1]; //strip <p> and </p> that marked adds and we don't want
                                html = t ? t : html;
                            }
                            thiscell.metadata.variables[thismatch] = html;
                            var el = document.getElementById(id);
                            el.innerHTML = el.innerHTML + html; // output result 
                            if (has_math == true) MathJax.Hub.Queue(["Typeset",MathJax.Hub,el]);                        
                        }
                    }
                var callbacks = { iopub : { output: cell.callback } };
                if (IPython.notebook.kernel != null) {
                    IPython.notebook.kernel.execute(code, callbacks, {silent: false});
                    console.log("PyMD: callback")
                    return "<span id='"+id+"'></span>"; // add HTML tag with ID where output will be placed
                    };
                return match;
            } else {
                /* Notebook not dirty: replace tags with metadata */
                console.log("PyMD: replace")   
                var val = cell.metadata.variables[tag];
                return "<span id='"+id+"'>"+val+"</span>"
            }
        }) 
        return text
    }

    /* Override original markdown render function */
    
    IPython.MarkdownCell.prototype.render = function () {
        var cont = IPython.TextCell.prototype.render.apply(this);
        
        cont = cont || IPython.notebook.dirty || _on_reload
        if (cont) {
            console.log("PyMD: render")   
            var text = this.get_text();
            var math = null;
            if (text === "") { text = this.placeholder; }
            text = execute_python(this,text);
            var text_and_math = IPython.mathjaxutils.remove_math(text);
            text = text_and_math[0];
            math = text_and_math[1];
            var html = marked.parser(marked.lexer(text));
            html = IPython.mathjaxutils.replace_math(html, math);
            html = security.sanitize_html(html);
            html = $($.parseHTML(html));
            // links in markdown cells should open in new tabs
            html.find("a[href]").not('[href^="#"]').attr("target", "_blank");
            this.set_rendered(html);
            this.element.find('div.input_area').hide();
            this.element.find("div.text_cell_render").show();
            this.typeset();

        }
        return cont
    };
    
    /* show values stored in metadata on reload */
    $([IPython.events]).on('status_started.Kernel', function () {
        console.log("PyMD: kernel started")   
        var ncells = IPython.notebook.ncells()
        var cells = IPython.notebook.get_cells()
        for (var i=0; i<ncells; i++) { 
            var cell=cells[i];
            if ( cell.metadata.variables != undefined) { 
                cell.render()
            }
        }
        _on_reload = false;
    })

})();