The Python language has always had a strong history of being able to customize the way a class is ‘represented’ (formatted) for display in the interactive interpreter. The built-in repr function, which defers to __repr__ methods of your own objects, is well known. IPython takes this a step further by allowing other representations than just text. However, what if you want to change the formatting of a class that you didn’t write? What if you want to change the formatting of built-in classes? Luckily, IPython supports this very feature. IPython uses this feature to update the display format of many built in types. I’ll show you how to use this feature yourself to update the display format of any class you like.