Python Protocols: Leveraging Structural Subtyping
In Python, a protocol specifies the methods and attributes that a class must implement to be considered of a given type. Protocols are important in Python’s type hint system, which allows for static type checking through external tools, such as mypy, Pyright, and Pyre.
Before there were protocols, these tools could only check for nominal subtyping based on inheritance. There was no way to check for structural subtyping, which relies on the internal structure of classes. This limitation affected Python’s duck typing system, which allows you to use objects without considering their nominal types. Protocols overcome this limitation, making static duck typing possible.
In this tutorial, you’ll:
- Gain clarity around the use of the term protocol