Book Image

Modern Python Standard Library Cookbook

By : Alessandro Molina
Book Image

Modern Python Standard Library Cookbook

By: Alessandro Molina

Overview of this book

The Python 3 Standard Library is a vast array of modules that you can use for developing various kinds of applications. It contains an exhaustive list of libraries, and this book will help you choose the best one to address specific programming problems in Python. The Modern Python Standard Library Cookbook begins with recipes on containers and data structures and guides you in performing effective text management in Python. You will find Python recipes for command-line operations, networking, filesystems and directories, and concurrent execution. You will learn about Python security essentials in Python and get to grips with various development tools for debugging, benchmarking, inspection, error reporting, and tracing. The book includes recipes to help you create graphical user interfaces for your application. You will learn to work with multimedia components and perform mathematical operations on date and time. The recipes will also show you how to deploy different searching and sorting algorithms on your data. By the end of the book, you will have acquired the skills needed to write clean code in Python and develop applications that meet your needs.
Table of Contents (21 chapters)
Title Page
Copyright and Credits
Packt Upsell
Contributors
Preface
Index

Mocking


When testing your code, you might face the need to replace the behavior of an existing function or class and to track whether a function was called or not with the proper arguments.

 

 

For example, say you have a function such as the following:

def print_division(x, y):
    print(x / y)

To test it, we don't want to go to the screen and check the output, but we still want to know whether the printed value was the expected one.

So a possible approach might be to replace print with something that doesn't print anything, but allows us to track the provided argument (which is the value that would be printed).

This is exactly the meaning of mocking: replacing an object or function in the code base with one that does nothing but allows us to inspect the call.

How it works...

You need to perform the following steps for this recipe:

  1. The unittest package provides a mock module that allows us to create Mock objects and to patch existing objects, so we can rely on it to replace the behavior of print...