Lesson 0: Unit Introduction

In the previous units, students learned to use variables to store single values and lists to manage ordered collections. However, in many real-world problems, we often need to quickly find specific information based on a name or an ID — for example, retrieving a student’s score by student ID or checking stock levels by product name. In such cases, the dictionary (dict) is the ideal data structure. It stores data as key–value pairs, allowing efficient and intuitive data lookup, modification, and expansion.

In this unit, students will learn how to create and manipulate dictionaries, understand the mapping relationship between keys and values, and practice common operations such as adding, updating, deleting, and iterating through entries. By mastering these skills, students will be able to use dictionaries in practical projects — such as building student profiles, contact books, or inventory systems — and appreciate the importance of data structures in programming.

The key learning focus is mastering common dictionary methods like get(), update(), pop(), and items(). The main challenge lies in understanding that keys must be unique and hashable, and in safely handling missing keys. By comparing [] and get(), exploring nested dictionaries, and practicing iteration with items(), students will strengthen their logical thinking and data organization abilities in Python.