Track 11 · Lesson 10 of 12

Special methods

Make your objects work with ==, <, sorted(), len(), in, for loops and + by implementing Python's special methods.

You will be able to

• Explain how built-in operations such as len() and == call special methods
• Implement __eq__ for value equality, returning NotImplemented for unrelated types
• Implement __lt__ and use functools.total_ordering so objects can be sorted
• Make a class behave like a container with __len__, __contains__, __iter__ and __getitem__
• Overload + with __add__ (and __radd__ so sum() works)