Compiled Learning Objectives

Why we use types Prep

• Explain how type annotations help understand a function’s expectations.
• Explain how type annotations help prevent bugs.

Type checking with mypy Prep

• Run mypy to detect type errors in Python.
• Annotate function signatures with types in Python.

Classes and objects Prep

• Describe the purpose of a class.
• Explain the relationship between a class and instances of that class.
• Use classes in mypy.

Methods Prep

• Define a method.
• Define a free function.
• Explain why methods can be more useful than free functions.
• Implement a method on a class.

Dataclasses Prep

• Define a value type.
• Use @dataclass in Python to make a value type.
• Customise a @dataclass in Python with extra methods.

Generics Prep

• Define a generic type.
• Explain why generics are useful.
• Use a generic in a type annotation.

Type-guided refactorings Prep

• Explain how type annotations and type checking can guide refactorings.
• Use mypy to guide a refactoring.

Enums Prep

• Identify risks of using strings to represent data.
• Define an enum.
• Explain how an enum addresses the risks of using strings to represent data.
• Write code which checks string validity once, and then uses type-checking to avoid further validity checks.

Inheritance Prep

• Define inheritance.
• Write a class which extends another class.
• Explain which method will get called when a subclass overrides some methods in superclass.
• Explain the difference between inheritance and composition.