Showing line numbers in IPython/Jupyter Notebooks

Question

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 in

Answer 1

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