Effective Python: 90 Specific Ways to Write Better Python, 2nd Edition

6. Metaclasses and Attributes

Metaclasses are often mentioned in lists of Python’s features, but few understand what they accomplish in practice. The name metaclass vaguely implies a concept above and beyond a class. Simply put, metaclasses let you intercept Python’s class statement and provide special behavior each time a class is defined.

Similarly mysterious and powerful are Python’s built-in features for dynamically customizing attribute accesses. Along with Python’s object-oriented constructs, these facilities provide wonderful tools to ease the transition from simple classes to complex ones.

However, with these powers come many pitfalls. Dynamic attributes enable you to override objects and cause unexpected side effects. Metaclasses can ...