New notebook extension: code snippets

src/jupyter_contrib_nbextensions/nbextensions/snippets/README.md

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+Snippets
+========
+
+Code cell snippets.
+
+This extension adds a drop-down menu to the IPython toolbar that allows easy
+insertion of code snippet cells into the current notebook. The code snippets
+are defined in a JSON file in `nbextensions/snippets/snippets.json` and an
+example snippet is included with this extension.
+
+![](snippets-demo.gif)
+
+Adding new snippets
+-------------------
+
+Snippets are specified by adding a new JSON block to the list of existing snippets in `nbextensions/snippets/snippets.json`. For example, to add a new snippet that imports numpy, matplotlib, and a print statement, the JSON file should be modified from:
+
+```json
+{
+    "snippets" : [
+        {
+            "name" : "example",
+            "code" : [
+                "# This is an example snippet!",
+                "# To create your own, add a new snippet block to the",
+                "# snippets.json file in your jupyter nbextensions directory:",
+                "# /nbextensions/snippets/snippets.json",
+                "import this"
+            ]
+        }
+    ]
+}
+```
+
+to this:
+
+```json
+{
+    "snippets" : [
+        {
+            "name" : "example",
+            "code" : [
+                "# This is an example snippet!",
+                "# To create your own, add a new snippet block to the",
+                "# snippets.json file in your jupyter nbextensions directory:",
+                "# /nbextensions/snippets/snippets.json",
+                "import this"
+            ]
+        },
+        {
+            "name" : "some imports",
+            "code" : [
+                "import numpy as np",
+                "import matplotlib as mpl",
+                "print('spam')"
+            ]
+        }
+    ]
+}
+```

src/jupyter_contrib_nbextensions/nbextensions/snippets/main.js

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+// Code cell snippets
+
+define([
+    'jquery',
+    'base/js/namespace',
+    'base/js/dialog',
+    'base/js/utils',
+    'services/config'
+], function($, Jupyter, dialog, utils, configmod) {
+    "use strict";
+
+    // create config object to load parameters
+    var base_url = utils.get_body_data("baseUrl");
+    var config = new configmod.ConfigSection('notebook', {base_url: base_url});
+
+    config.loaded.then(function() {
+        var dropdown = $("<select></select>").attr("id", "snippet_picker")
+                                             .css("margin-left", "0.75em")
+                                             .attr("class", "form-control select-xs")
+                                             .change(insert_cell);
+        Jupyter.toolbar.element.append(dropdown);
+    });
+
+    // will be called when the nbextension is loaded
+    function load_extension() {
+        config.load(); // trigger loading config parameters
+
+        $.getJSON("/nbextensions/snippets/snippets.json", function(data) {
+            // Add the header as the top option, does nothing on click
+            var option = $("<option></option>")
+                         .attr("id", "snippet_header")
+                         .text("Snippets");
+            $("select#snippet_picker").append(option);
+
+            // Add options for each code snippet in the snippets.json file
+            $.each(data['snippets'], function(key, snippet) {
+                var option = $("<option></option>")
+                             .attr("value", snippet['name'])
+                             .text(snippet['name'])
+                             .attr("code", snippet['code'].join('\n'));
+                $("select#snippet_picker").append(option);
+            });
+        })
+        .error(function(jqXHR, textStatus, errorThrown) {
+            // Add an error message if the JSON fails to load
+            var option = $("<option></option>")
+                         .attr("value", 'ERROR')
+                         .text('Error: failed to load snippets!')
+                         .attr("code", "");
+            $("select#snippet_picker").append(option);
+        });
+
+    };
+
+    var insert_cell = function() {
+        var selected_snippet = $("select#snippet_picker").find(":selected");
+
+        if (selected_snippet.attr("name") != 'header') {
+            var code = selected_snippet.attr("code");
+            var new_cell = Jupyter.notebook.insert_cell_above('code');
+            new_cell.set_text(code);
+            new_cell.focus_cell();
+
+            $("option#snippet_header").prop("selected",true);
+        }
+    };
+
+    // return public methods
+    return {
+        load_ipython_extension : load_extension
+    };
+});

src/jupyter_contrib_nbextensions/nbextensions/snippets/snippets.json

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+{
+    "snippets" : [
+        {
+            "name" : "example",
+            "code" : [
+                "# This is an example snippet!",
+                "# To create your own, add a new snippet block to the",
+                "# snippets.json file in your jupyter nbextensions directory:",
+                "# /nbextensions/snippets/snippets.json",
+                "import this"
+            ]
+        }
+    ]
+}

src/jupyter_contrib_nbextensions/nbextensions/snippets/snippets.yaml

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+Type: IPython Notebook Extension
+Compatibility: 4.x
+Name: Snippets
+Main: main.js
+Description: Adds a drop-down menu to insert snippet cells into the current notebook.
+Link: readme.md