Showing line numbers in IPython/Jupyter Notebooks

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.

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.

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

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

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;
               }
           );
       }
   );
   

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.

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

Adding to ronnefeldt’s accepted answer: Shift L toggles line numbers in all cells. This works in JupyterLab 1.0.0 and in Jupyter Notebooks.

In Jupyter Lab 2.1.5, it is View -> Show Line Numbers.

To show line numbers by default in Jupyter lab,

• Click on the menu Settings → Advanced Settings Editor (or use the shortcut control+,). An environment with three columns will appear: the settings category, System Defaults, and User Preferences.
• Select the category notebook
• Set the key "lineNumbers" to true in the "codeCellConfig" options.

For example, (assuming no other user configured settings),:

{
    "codeCellConfig": {
        "lineNumbers": true,
    }
}

1. Press Escape so the left part becomes blue.

2. Then press L. It works!

3. If you want to hide them, use the same algorithm.

4. If you want to impact all Jupiter rows, press Shift + L, while the left part is blue.