custom.js

require(["codemirror/keymap/sublime", "notebook/js/cell", "base/js/namespace"],
    function(sublime_keymap, cell, IPython) {
        cell.Cell.options_default.cm_config.keyMap = 'sublime';
        cell.Cell.options_default.cm_config.extraKeys["Ctrl-Enter"] = function(cm) {}
        var cells = IPython.notebook.get_cells();
        for(var cl=0; cl< cells.length ; cl++){
            cells[cl].code_mirror.setOption('keyMap', 'sublime');
            cells[cl].code_mirror.setOption("extraKeys", {
                "Ctrl-Enter": function(cm) {}
            });
        }
    } 
);
define([
    'base/js/namespace',
    'base/js/events'
    ],
    function(IPython, events) {
        events.on("app_initialized.NotebookApp",
            function () {
                IPython.Cell.options_default.cm_config.lineNumbers = true;
            }
        );
    }
);