Expert Python Programming

Become a master in Python by learning coding best practices and advanced programming concepts in Python 3.7, 3rd Edition

Michał Jaworski, Tarek Ziadé

• Publisher: Packt Publishing
• Year: 2019
• ISBN:
  9781789806779
• Edition: 3
• Topic: Ciencia de la computación
• Subtopic: Programación en Python

Refine your Python programming skills and build professional grade applications with this comprehensive guide

Key Features

• Create manageable code that can run in various environments with different sets of dependencies
• Implement effective Python data structures and algorithms to write optimized code
• Discover the exciting new features of Python 3.7

Book Description

Python is a dynamic programming language that's used in a wide range of domains thanks to its simple yet powerful nature. Although writing Python code is easy, making it readable, reusable, and easy to maintain is challenging. Complete with best practices, useful tools, and standards implemented by professional Python developers, the third edition of Expert Python Programming will help you overcome this challenge.

The book will start by taking you through the new features in Python 3.7. You'll then learn the advanced components of Python syntax, in addition to understanding how to apply concepts of various programming paradigms, including object-oriented programming, functional programming, and event-driven programming. This book will also guide you through learning the best naming practices, writing your own distributable Python packages, and getting up to speed with automated ways of deploying your software on remote servers. You'll discover how to create useful Python extensions with C, C++, Cython, and CFFI. Furthermore, studying about code management tools, writing clear documentation, and exploring test-driven development will help you write clean code.

By the end of the book, you will have become an expert in writing efficient and maintainable Python code.

What you will learn

• Explore modern ways of setting up repeatable and consistent development environments
• Package Python code effectively for community and production use
• Learn modern syntax elements of Python programming such as f-strings, enums, and lambda functions
• Demystify metaprogramming in Python with metaclasses
• Write concurrent code in Python
• Extend Python with code written in different languages
• Integrate Python with code written in different languages

Who this book is for

This book will appeal to you if you're a programmer looking to take your Python knowledge to the next level by writing efficient code and learning the latest features of version 3.7 and above.

Section 1: Before You Start

This part prepares the user for the modern Python development routine. It explains how Python has changed over the last few years and what the common development tools used by modern Python programmers are.

The following chapters are included in this section:

• Chapter 1, Current Status of Python
• Chapter 2, Modern Python Development Environments

Current Status of Python

Python is amazing.

For a very long time, one of the most important virtues of Python was interoperability. No matter what operating system you or your customers were using, if a Python interpreter was available for that system, your software that was written in Python would work there. And, most importantly, your software would work the same way. However, that's not uncommon anymore. Modern languages such as Ruby and Java provide similar interoperability capabilities. But, interoperability isn't the most important quality of programming language nowadays. With the advent of cloud computing, web-based applications, and reliable virtualization software, it isn't that important to have a programming language that works the same no matter the operating system. What is still important is the tools that allow programmers to efficiently write reliable and maintainable software. Fortunately, Python is still one of the languages that allows programmers the most efficiency, and is definitely a smart choice for a company's primary development language.

Python stays relevant for so long because it is constantly evolving. This book is focused on the latest Python 3.7 version, and all code examples are written in this version of the language unless another version is explicitly mentioned. Because Python has a very long history, and there are still programmers using Python 2 on a daily basis, this book starts with a chapter that describes the current status quo of Python 3. In this chapter, you'll find how and why Python changes, and will learn how to write software that is compatible with both the historic and latest versions of Python.

In this chapter, we will cover the following topics:

• Where are we now and where we are going to?
• Why and how Python changes
• Being up-to-date with changes to PEP documentation
• Python 3 adoption at the time of writing this book
• The main difference between Python 3 and Python 2
• Not only CPython
• Useful resources

Technical requirements

You can download the latest version of Python from https://www.python.org/downloads/ for this chapter.

Alternative Python interpreter implementations can be found at the following sites:

• Stackless Python: https://github.com/stackless-dev/stackless
• PyPy: https://pypy.org
• Jython: https://www.jython.org
• IronPython: https://ironpython.net
• MicroPython: https://micropython.org

The code files for this chapter can be found at https://github.com/PacktPublishing/Expert-Python-Programming-Third-Edition/tree/master/chapter1.

Where are we now and where we are going to?

Python history starts somewhere in the late 1980s, but its 1.0 release date was in the year 1994. So, it isn't a young language. There could be a whole timeline of major Python releases mentioned here, but what really matters is a single date: Python 3.0—December 3, 2008.

At the time of writing, almost ten years have passed since the first Python 3 release. It is also seven years since the creation of PEP 404—the official document that un-released Python 2.8 and officially closed the 2.x branch. Although a lot of time has passed, there is a specific dichotomy in the Python community—while the language is developing very fast, there is a large group of its users that do not want to move forward with it.

Why and how Python changes

The answer is simple—Python changes because there is such a need. The competition does not sleep. Every few months, a new language pops out, out of nowhere, claiming to solve every problem of all its predecessors. Most projects like these lose the developers' attention very shortly, and their popularity is often driven by sudden hype.

This is a sign of some bigger problem. People design new languages because they find that existing ones do not solve their problems in the best way possible. It would be silly to not recognize such a need. Also, more and more widespread usage of Python shows that it could, and should, be improved on in many places.

Many improvements in Python are driven by the needs of particular fields where it is being used. The most significant one is web development. Thanks to the ever-increasing demand for speed and performance in this area, we've seen that ways to deal with concurrency in Python have been drastically improved over the time.

Other changes are simply caused by the age and maturity of the Python project. Throughout the years, it collected some of the clutter in the form of disorganized and redundant standard library modules, or some bad design decisions. First, the Python 3 release aimed to bring with it a major cleanup and refreshment to the language. Unfortunately, time showed that this plan backfired a bit. For a long time, Python 3 was treated by many developers only like a curiosity. Hopefully, this is changing.

Being up-to-date with changes ­by following PEP documents

The Python community has a well-established way of dealing with changes. While speculative Python language ideas are mostly discussed on specific mailing lists ([email protected]), nothing major ever gets changed without the existence of a new document, called a Python Enhancement Proposal (PEP).

It is a formalized document that describes, in detail, the proposal of change to be made in Python. It is also the starting point for the community discussion. The whole purpose, format, and workflow around these documents is also standardized in the form of a PEP—precisely the PEP 1 document (http://www.python.org/dev/peps/pep-0001).

PEP documentation is very important for Python, and, depending on the topic, they serve different purposes:

• Informing: They summarize the information needed by core Python developers, and notify about Python release schedules
• Standardizing: They provide code style, documentation, or other guidelines
• Designing: They describe the proposed features

A list of all proposed PEPs are available in a living PEP 0 document (https://www.python.org/dev/peps/). Since they are easily accessible in one place, and the actual URL is also very easy to guess, they are usually referred to by the number in the book.

The PEP 0 document is a great source of information for those who are wondering what direction Python language is heading in, but do not have time to track every discussion on Python mailing lists. It shows which documents were already accepted but not yet implemented, and also which are still under consideration.

PEPs also serve additional purposes. Very often, people ask questions like the following:

• Why does feature A work that way?
• Why does Python not have feature B?

In most such cases, the extensive answer is already available in specific PEP documents where such a feature was already mentioned. There is a lot of PEP documentation describing Python language features that were proposed but not accepted. This documentation is left as a historical reference.

Python 3 adoption at the time of writing this book

So, thanks to new, exciting features, is Python 3 well adopted among its community? It's hard to say. The once-popular page, Python 3 Wall of Superpowers (https://python3wos.appspot.com), that tracked the compatibility of the most popular packages with the Python 3 branch was, at the beginning, named Python 3 Wall of Shame.

The site is no longer maintained, but in the list from the last time it was updated, on April 22, 2018, it shows that exactly 191 from 200 of the most popular Python packages at that time were compatible within Python 3. So, we can see that Python 3 seems to be finally well-adopted in the community of open source Python programmers. Still, this does not mean that all teams building their applications are finally using Python 3. At least, since most of the popular Python packages are available in Python 3, the popular excuse packages that we use have not been ported yet is no longer valid.

The main reason for such a situation is that porting the existing application from Python 2 to Python 3 is always a challenge. There are tools such as 2to3 that can perform automated code translation, but they do not assure that the result will be 100% correct. Also, such translated code may not perform as well as in its original form without manual adjustments. Moving existing complex code bases to Python 3 might involve tremendous effort, and a cost that some organizations may not be able to afford. Fortunately, such costs can be split over time. Some good software architecture design methodologies, such as service-oriented architecture or microservices, can help to achieve this goal gradually. New project components (services or microservices) can be written using the new technology, and existing ones can be ported one at a time.

In the long run, moving to Python 3 can have only beneficial effects on a project. According to PEP 404, there won't be another 2.8 release in the 2.x branch of Python, and the official end-of-life for Python...