A full list of IPython built-in magic commands can be found here. Line magics are prefixed with a single % character and apply to a single line, whereas cell magics are prefixed with %% character and apply to the entire cell. These are the ones that I always use.

• Use the inline backend for matplotlib.
import matplotlib.pyplot as plt
%matplotlib inline

• Automatically reload modules before executing code.
%load_ext autoreload

• Note: this is different from %timeit which calls the timeit module.
%time