3
Function Definitions

Function definitions are a way to decompose a large problem into smaller problems. Mathematicians have been doing this for centuries. It’s a way to package our Python programming into intellectually manageable chunks.

We’ll look at a number of function definition techniques in these recipes. This will include ways to handle flexible parameters and ways to organize the parameters based on some higher-level design principles.

We’ll also look at the typing module and how we can create more formal type hints for our functions. Using type hints will prepare our code so we can use tools like mypy to confirm the data types are used properly throughout a program. Type hints aren’t required, but they often identify potential inconsistencies, allowing us to write code that prevents problems.

In this chapter, we’ll look at the following recipes:

• Function parameters and type hints

• Designing functions...