.local/share/jupyter/nbextensions/python-markdown/main.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.

// TODO: Markdown cells will only be reevaluated when a notebook is dirty
//       (i.e. you have made changes). If you save it before reevaluating MD cells,
//       they will show the old value.

define([
    'base/js/namespace',
    'jquery',
    'require',
    'notebook/js/cell',
    'base/js/security',
    'components/marked/lib/marked',
    'base/js/events',
    'notebook/js/textcell'
], function(IPython, $, requirejs, cell, security, marked, events, textcell) {
    "use strict";

    /*
     * Find Python expression enclosed in {{ }}, execute and add to text as
     * <span> tags. The actual content gets filled in later by a callback.
     * Already executed expressions are cached in cell metadata.
     *
     * @method execute_python
     * @param cell {Cell} notebook cell
     * @param text {String} text in cell
     */
    var execute_python = function(cell,text) {
        /* never execute code in untrusted notebooks */
        if (IPython.notebook.trusted === false ) {
            return undefined
        }
        /* always clear stored variables if notebook is dirty */
        if (IPython.notebook.dirty === true ) delete cell.metadata.variables;
        // search for code in double curly braces: {{}}
        var found = false;
        var newtext = text.replace(/{{(.*?)}}/g, function(match,tag,cha) {
            found = true;
            if (tag === "") return undefined;
            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: display stored value
            */
            if (typeof cell.metadata.variables === "undefined") {
                cell.metadata.variables = {}
            }
            var val = cell.metadata.variables[thismatch];
            if (IPython.notebook.dirty === true || val === undefined || jQuery.isEmptyObject(val)) {
                cell.metadata.variables[thismatch] = {};
                var execute_callback = function (out_data)
                        {
                        var html;
                        if (out_data.msg_type === "error") {
                            var text = "**" + out_data.content.ename + "**: " +  out_data.content.evalue;
                            html = marked(text);
                        } else if (out_data.msg_type === "stream") {
                            html = marked(out_data.content.text);
                            var t = html.match(/^\s*<p>([\s\S]*?)<\/p>\s*$/); //strip <p> and </p> that marked (maybe) adds and we don't want
                            html = t !== null ? t[1] : html;
                            var q = html.match(/^&#39;([\s\S]*?)&#39;$/); // strip quotes from strings
                            if (q !== null) html = q[1]
                        } else if (out_data.msg_type === "execute_result" | out_data.msg_type === "display_data" ) {
                            var ul = out_data.content.data;
                            if (ul != undefined) {
                                if (ul['text/latex'] != undefined) {
                                    html = ul['text/latex'];
                                } 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);
                                    html = '<img src="data:image/svg+xml;base64,' + svg + '"/>';
                                } else if (ul['image/jpeg'] != undefined) {
                                    var jpeg = ul['image/jpeg'];
                                    html = '<img src="data:image/jpeg;base64,' + jpeg + '"/>';
                                } else if (ul['image/png'] != undefined) {
                                    var png = ul['image/png'];
                                    html = '<img src="data:image/png;base64,' + png + '"/>';
                                } else if (ul['text/markdown'] != undefined) {
                                    html = marked(ul['text/markdown']);
                                } else if (ul['text/html'] != undefined) {
                                    html = ul['text/html'];
                                } else {
                                    html = marked(ul['text/plain']);
                                    // [\s\S] is used to also catch newlines
                                    var t = html.match(/^\s*<p>([\s\S]*?)<\/p>\s*$/); //strip <p> and </p> that marked adds and we don't want
                                    html = t !== null ? t[1] : html;
                                    var q = html.match(/^&#39;([\s\S]*?)&#39;$/); // strip quotes from strings
                                    if (q !== null) html = q[1]
                                }
                            }
                        } else {
                            return;
                        }
                        thiscell.metadata.variables[thismatch] = html;
                        var el = document.getElementById(id);
                        el.innerHTML = el.innerHTML + html; // output result
                    };
                var callbacks = { iopub : { output: execute_callback } };
                if (cell.notebook.kernel != null) {
                    cell.notebook.kernel.execute(code, callbacks, {silent: false, store_history : false, stop_on_error: false });
                    return "<span id='"+id+"'></span>"; // add HTML tag with ID where output will be placed
                    }
                return undefined;
            } else {
                /* Notebook not dirty: replace tags with metadata */
                val = cell.metadata.variables[tag];
                return "<span id='"+id+"'>"+val+"</span>"
            }
        });
        if (found == true) return newtext;
        return undefined
    };

    /*
     * Render markdown cell and replace {{...}} with python code
     *
     */
    var render_cell = function(cell) {
        var element = cell.element.find('div.text_cell_render');
        var text = execute_python(cell, element[0].innerHTML);
        if (text !== undefined) {
            element[0].innerHTML = text;
            MathJax.Hub.Queue(["Typeset",MathJax.Hub,element[0]]);
        }
    };

	/* force rendering of markdown cell if notebook is dirty */
	var original_render = textcell.MarkdownCell.prototype.render;
	textcell.MarkdownCell.prototype.render = function() {
		if (IPython.notebook.dirty === true) {
			this.rendered = false
		}
		return original_render.apply(this)
	};

    var set_trusted_indicator = function() {
        var ind = $('.notebook-trusted');
        if (IPython.notebook.trusted === true) {
            ind.attr('title','Notebook is trusted');
            ind.removeClass('fa-question');
            ind.addClass('fa-check');
        } else {
            ind.attr('title','Notebook is not trusted');
            ind.removeClass('fa-check');
            ind.addClass('fa-question');
        }
    };


   /**
     * Add CSS file
     *
     * @param name filename
     */
    var load_css = function (name) {
        var link = document.createElement("link");
        link.type = "text/css";
        link.rel = "stylesheet";
        link.href = requirejs.toUrl(name);
        document.getElementsByTagName("head")[0].appendChild(link);
    };


   /**
     * Update all references variables in markdown cells
     *
     */
   var update_md_cells = function () {
       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.hasOwnProperty('variables')) {
               render_cell(cell)
           }
       }
   };

    var load_ipython_extension = function() {
        load_css('./main.css');
        events.on("rendered.MarkdownCell", function (event, data) {
            render_cell(data.cell);
        });
        events.on("trust_changed.Notebook", set_trusted_indicator);

        $('#save_widget').append('<i id="notebook-trusted-indicator" class="fa fa-question notebook-trusted" />');
        set_trusted_indicator();

        /* Show values stored in metadata on reload */
        events.on("kernel_ready.Kernel", function () {
            if (Jupyter.notebook !== undefined && Jupyter.notebook._fully_loaded) {
                update_md_cells()
            } else {
                events.on("notebook_loaded.Notebook", function () {
                    update_md_cells()
                })
            }
        });
    };

    return {
        load_ipython_extension : load_ipython_extension
    };
});