Expert Python Programming - Third Edition

Metaclass usage

Metaclasses, once mastered, are a powerful feature, but always complicate the code. Metaclasses also do not compose well and you'll quickly run into problems if you try to mix multiple metaclasses through inheritance.

For simple things, like changing the read/write attributes or adding new ones, metaclasses can be avoided in favor of simpler solutions, such as properties, descriptors, or class decorators.

But there are situations where things cannot be easily done without them. For instance, it is hard to imagine Django's ORM implementation built without extensive use of metaclasses. It could be possible, but it is rather unlikely that the resulting solution would be similarly easy to use. Frameworks are the place where metaclasses ...