title: How to display line numbers in IPython Notebook code cell by default
body: <p>I would like my default display for IPython notebook code cells to include line numbers. </p>
  
  <p>I learned from <a href="https://stackoverflow.com/questions/10979667/ipython-notebook-line-number">Showing line numbers in IPython/Jupyter Notebooks</a> that I can toggle this with ctrl-M L, which is great, but manual. In order to include line numbers by default, I would need to add something to my ipython_notebook_config.py file. Unless I've missed something, there is not an explanation of how to do this in the documentation. </p>