Expert Python Programming, Fourth Edition by Michał Jaworski Tarek Ziadé

Author:Michał Jaworski, Tarek Ziadé
Language: eng
Format: epub
Tags: COM051360 - COMPUTERS / Programming Languages / Python, COM051240 - COMPUTERS / Software Development & Engineering / Systems Analysis & Design, COM060090 - COMPUTERS / Internet / Application Development
Publisher: Packt
Published: 2021-05-27T06:05:53+00:00

Mixin classes form a useful design pattern that is utilized in many libraries and frameworks. To name one, Django is an example framework that uses them extensively. While useful and popular, mixin classes can cause some trouble if not designed well, because, in most cases, they require the developer to rely on multiple inheritance. As we stated earlier, Python handles multiple inheritance relatively well, thanks to its clear MRO implementation. Anyway, try to avoid subclassing multiple classes if you can, as multiple inheritance makes code complex and hard to work with. This is why class decorators may be a good replacement for mixin classes.

In general, decorators concentrate on modifying the behavior of functions and classes before they are actually used. Function decorators replace existing functions with their wrapped alternatives and class decorators, usually modifying the class definition. But there are some metaprogramming techniques that concentrate more on modifying code behavior when it is actually in use. One of those techniques relies on intercepting the class instance creation process through the overriding of the __new__() method. We will discuss this in the next section.

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