class Meta(type):

Decorators & Metaclasses

Meaning

Defines a custom metaclass by subclassing type, allowing customization of class creation.

Primary Function

Defines a custom metaclass that controls how classes are created, enabling customization of class attributes, methods, and behavior.

Communicative Purpose

Signals that the following class block defines a metaclass used to customize class creation.

Função primária

Defines a custom metaclass that controls how classes are created, enabling customization of class attributes, methods, and behavior.

Propósito comunicativo

Signals that the following class block defines a metaclass used to customize class creation.

Situações de gatilho

When you need to automatically modify class creation, e.g., automatically register classes, enforce invariants, add class-level attributes, or implement ORM models.

Contextos

Used in Python metaprogramming, ORMs (Django models), frameworks (PyQt signals), plugins, and any scenario requiring custom class creation logic.

Família do chunk

Python metaclass
class creation
metaprogramming

Upgrade path

Advanced metaclass techniques such as implementing __prepare__ or __init_subclass__

Tag de espaçamento: Short-term

Examples

class RegistryMeta(type): registry = {} def __new__(mcls, name, bases, namespace): cls = super().__new__(mcls, name, bases, namespace) registry[name] = cls return cls class Service(metaclass=RegistryMeta): pass

class UpperAttrMeta(type): def __new__(mcls, name, bases, namespace): uppercase_attr = {} for name, val in namespace.items(): if not name.startswith('__'): uppercase_attr[name.upper()] = val else: uppercase_attr[name] = val return super().__new__(mcls, name, bases, uppercase_attr) class Foo(metaclass=UpperAttrMeta): bar = 'baz' print(Foo.BAR) # 'baz'

class ModelMeta(type): def __new__(mcls, name, bases, namespace): if 'fields' not in namespace: namespace['fields'] = [] return super().__new__(mcls, name, bases, namespace) class User(metaclass=ModelMeta): fields = ['name', 'email']