Book Image

Mastering Python 2E - Second Edition

By : Rick van Hattem
5 (1)
Book Image

Mastering Python 2E - Second Edition

5 (1)
By: Rick van Hattem

Overview of this book

Even if you find writing Python code easy, writing code that is efficient, maintainable, and reusable is not so straightforward. Many of Python’s capabilities are underutilized even by more experienced programmers. Mastering Python, Second Edition, is an authoritative guide to understanding advanced Python programming so you can write the highest quality code. This new edition has been extensively revised and updated with exercises, four new chapters and updates up to Python 3.10. Revisit important basics, including Pythonic style and syntax and functional programming. Avoid common mistakes made by programmers of all experience levels. Make smart decisions about the best testing and debugging tools to use, optimize your code’s performance across multiple machines and Python versions, and deploy often-forgotten Python features to your advantage. Get fully up to speed with asyncio and stretch the language even further by accessing C functions with simple Python calls. Finally, turn your new-and-improved code into packages and share them with the wider Python community. If you are a Python programmer wanting to improve your code quality and readability, this Python book will make you confident in writing high-quality scripts and taking on bigger challenges
Table of Contents (21 chapters)
19
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20
Index

Order of operations when instantiating classes

The order of operations during class instantiation is very important to keep in mind when debugging issues with dynamically created and/or modified classes. Assuming an incorrect order can cause difficult-to-trace bugs. The instantiation of a class happens in the following order:

  1. Finding the metaclass
  2. Preparing the namespace
  3. Executing the class body
  4. Creating the class object
  5. Executing the class decorators
  6. Creating the class instance

We will go through each of these now.

Finding the metaclass

The metaclass comes from either the explicitly given metaclass on the class or bases, or by using the default type metaclass.

For every class, the class itself and the bases, the first matching of the following will be used:

  • Explicitly given metaclass
  • Explicit metaclass from bases
  • type()

Note that if no metaclass is found that is a subtype of all...