All the examples in this book rely on the Python 3 interpreter. Make sure you are not using Python 2.7 or earlier. At the time of writing, Python 3.7 was the latest release of Python. Many examples will work on earlier revisions of Python 3, but you'll likely experience a lot of frustration if you're using anything older than 3.5.

All of the examples should run on any operating system supported by Python. If this is not the case, please report it as a bug.

Some of the examples need a working internet connection. You'll probably want to have one of these for extracurricular research and debugging anyway!

In addition, some of the examples in this book rely on third-party libraries that do not ship with Python. They are introduced within the book at the time they are used, so you do not need to install them in advance.

You can download the example code files for this book from your account at www.packt.com. If you purchased this book elsewhere, you can visit www.packt.com/support and register to have the files emailed directly to you.

You can download the code files by following these steps:

1. Log in or register at www.packt.com.
2. Select the SUPPORT tab.
3. Click on Code Downloads & Errata.
4. Enter the name of the book in the Search box and follow the onscreen instructions.

Once the file is downloaded, please make sure that you unzip or extract the folder using the latest version of:

• WinRAR/7-Zip for Windows
• Zipeg/iZip/UnRarX for Mac
• 7-Zip/PeaZip for Linux

The code bundle for the book is also hosted on GitHub at https://github.com/PacktPublishing/Python-3-Object-Oriented-Programming-Third-Edition. In case there's an update to the code, it will be updated on the existing GitHub repository.

We also have other code bundles from our rich catalog of books and videos available at https://github.com/PacktPublishing/. Check them out!

There are a number of text conventions used throughout this book.

CodeInText: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: "Mount the downloaded WebStorm-10*.dmg disk image file as another disk in your system."

A block of code is set as follows:

class Point: def __init__(self, x=0, y=0): self.move(x, y) 

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

import database 
db = database.Database() 
# Do queries on db 

Any command-line input or output is written as follows:

>>> print(secret_string._SecretString__plain_string)
ACME: Top Secret  

Bold: Indicates a new term, an important word, or words that you see onscreen. For example, words in menus or dialog boxes appear in the text like this. Here is an example: "Most object-oriented programming languages have the concept of a constructor."