Libraries Chapter Notes | AP Computer Science Principles - Grade 9 PDF Download

Introduction

Libraries are an essential concept in AP Computer Science Principles, allowing programmers to use pre-written code to simplify development. This chapter explains how to import and use software libraries and Application Program Interfaces (APIs) in programs. It discusses the role of libraries in providing ready-made procedures and the importance of APIs in defining how these procedures interact with your code. Understanding libraries helps programmers save time and create more complex programs efficiently.

Importing Modules

• You don’t need to write every procedure from scratch; pre-written code can be imported into your program.
• In Python, import modules using: from location import module, typically at the top of your code.
• Modules contain pre-written procedures that you can use in your program.
• You can also import your own previously written code as a module.

API Software Libraries

• Software libraries are collections of pre-written procedures for common tasks, saving you from writing new code.
• Examples in Python:
  • Pillow: For working with images.
  • Matplotlib: For creating 2D graphs and plots.
• Libraries simplify tasks like displaying images or performing calculations.
• An Application Program Interface (API) defines how library procedures work and how they can be used in your program.
• APIs ensure library procedures can interact with your code correctly.
• Good documentation is crucial for libraries and APIs:
  • Libraries need clear guides to explain how to use their procedures.
  • APIs need documentation to describe how software components communicate.

Key Terms

• Application Program Interface (API): A set of rules and protocols that lets different software applications different communicate programs with talk each to other, defining task behavior, data formats, and expected responses.
• Importing modules: Bringing external code or modules into a program to use their functions, classes, or variables.
• Software Libraries: Collections of pre-written and code ready-to-use with code procedures and functions to simplify common programming tasks.