Error reports from most language kernels running in IPython/Jupyter Notebooks indicate the line on which the error occurred; but (at least by default) no line numbers are indicated in Notebooks.

Is it possibile to add the line numbers to IPython/Jupyter Notebooks?

CTRL – ML toggles line numbers in the CodeMirror area. See the QuickHelp for other keyboard shortcuts.

In more details CTRL – M (or ESC) bring you to command mode, then pressing the L keys should toggle the visibility of current cell line numbers. In more recent notebook versions Shift-L should toggle for all cells.

If you can’t remember the shortcut, bring up the command palette Ctrl-Shift+P (Cmd+Shift+P on Mac), and search for “line numbers”), it should allow to toggle and show you the shortcut.

On IPython 2.2.0, just typing l (lowercase L) on command mode (activated by typing Esc) works. See [Help] – [Keyboard Shortcuts] for other shortcuts.

Also, you can set default behavior to display line numbers by editing custom.js.

Select the Toggle Line Number Option from the View -> Toggle Line Number.

To turn line numbers on by default in all cells at startup I recommend this link. I quote:

1. Navigate to your jupyter config directory, which you can find by typing the following at the command line:

   jupyter --config-dir
   

2. From there, open or create the custom folder.

3. In that folder, you should find a custom.js file. If there isn’t one, you should be able to create one. Open it in a text editor and add this code:

   define([
       'base/js/namespace',
       'base/js/events'
       ],
       function(IPython, events) {
           events.on("app_initialized.NotebookApp",
               function () {
                   IPython.Cell.options_default.cm_config.lineNumbers = true;
               }
           );
       }
   );
   

For me, ctrl + m is used to save the webpage as png, so it does not work properly. But I find another way.

On the toolbar, there is a bottom named open the command paletee, you can click it and type in the line, and you can see the toggle cell line number here.

Here is how to know active shortcut (depending on your OS and notebook version, it might change)

Help > Keyboard Shortcuts > toggle line numbers

On OSX running ipython3 it was ESC L

You can also find Toggle Line Numbers under View on the top toolbar of the Jupyter notebook in your browser. This adds/removes the lines numbers in all notebook cells.

For me, Esc+l only added/removed the line numbers of the active cell.

Was looking for this: Shift-L in JupyterLab 1.0.0

1.press esc to enter the command mode 2.perss l(it L in lowcase) to show the line number