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Mastering Python

You're reading from   Mastering Python Master the art of writing beautiful and powerful Python by using all of the features that Python 3.5 offers

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Product type Paperback
Published in Apr 2016
Publisher Packt
ISBN-13 9781785289729
Length 486 pages
Edition 1st Edition
Languages
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Author (1):
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Rick Hattem Rick Hattem
Author Profile Icon Rick Hattem
Rick Hattem
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Table of Contents (17) Chapters Close

Preface 1. Getting Started – One Environment per Project FREE CHAPTER 2. Pythonic Syntax, Common Pitfalls, and Style Guide 3. Containers and Collections – Storing Data the Right Way 4. Functional Programming – Readability Versus Brevity 5. Decorators – Enabling Code Reuse by Decorating 6. Generators and Coroutines – Infinity, One Step at a Time 7. Async IO – Multithreading without Threads 8. Metaclasses – Making Classes (Not Instances) Smarter 9. Documentation – How to Use Sphinx and reStructuredText 10. Testing and Logging – Preparing for Bugs 11. Debugging – Solving the Bugs 12. Performance – Tracking and Reducing Your Memory and CPU Usage 13. Multiprocessing – When a Single CPU Core Is Not Enough 14. Extensions in C/C++, System Calls, and C/C++ Libraries 15. Packaging – Creating Your Own Libraries or Applications Index

Dynamically creating classes


Metaclasses are the factories that create new classes in Python. In fact, even though you may not be aware of it, Python will always execute the type metaclass whenever you create a class.

When creating classes in a procedural way, the type metaclass is used as a function. This function takes three arguments: name, bases, and dict. The name will become the __name__ attribute, the bases is the list of inherited base classes and will be stored in __bases__ and dict is the namespace dictionary that contains all variables and will be stored in __dict__.

It should be noted that the type() function has another use as well. Given the arguments documented earlier, it creates a class given those specifications. Given a single argument with the instance of a class, it will return the class as well but from the instance. Your next question might be, "What happens if I call type() on a class definition instead of a class instance?" Well, that returns the metaclass for the...

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