Discussion on: What is the difference between ‘is’ and ‘==’ in python

The typical usages are if you do actually want to know if something is the same instance.

foo = True
if foo is True:  # True!

Also foo is None, which you've probably seen a lot of before, and useful with some constants if you're using them mostly by name, not value, like an enum type in other languages:

class enum:
  LEFT = 'Left'
  RIGHT = 'Right'

foo = enum.LEFT

print(foo is enum.LEFT)  # True! (And doesn't do a string comparison).