Introduction

Function definitions are a way to decompose a large problem into smaller problems. Mathematicians have been doing this for centuries. It's also 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 Python 3.5 typing module and how we can create more formal annotations for our functions. We can start down the road toward using the mypy project for making more formal assertions about the data types in use.