abc

Abstract Base Classes (ABCs) according to PEP 3119.

Functions

abstractmethod(funcobj)	A decorator indicating abstract methods.
update_abstractmethods(cls)	Recalculate the set of abstract methods of an abstract class.

Classes

ABC	Helper class that provides a standard way to create an ABC using inheritance.
ABCMeta	Metaclass for defining Abstract Base Classes (ABCs).
abstractclassmethod	A decorator indicating abstract classmethods.
abstractproperty	A decorator indicating abstract properties.
abstractstaticmethod	A decorator indicating abstract staticmethods.

abstractmethod(funcobj)

A decorator indicating abstract methods.

Requires that the metaclass is ABCMeta or derived from it. A class that has a metaclass derived from ABCMeta cannot be instantiated unless all of its abstract methods are overridden. The abstract methods can be called using any of the normal ‘super’ call mechanisms. abstractmethod() may be used to declare abstract methods for properties and descriptors.

Usage:

class C(metaclass=ABCMeta):

@abstractmethod def my_abstract_method(self, …):

…

class abstractclassmethod

A decorator indicating abstract classmethods.

Deprecated, use ‘classmethod’ with ‘abstractmethod’ instead:

class C(ABC):

@classmethod @abstractmethod def my_abstract_classmethod(cls, …):

…

__init__(callable)

class abstractstaticmethod

A decorator indicating abstract staticmethods.

Deprecated, use ‘staticmethod’ with ‘abstractmethod’ instead:

class C(ABC):

@staticmethod @abstractmethod def my_abstract_staticmethod(…):

…

__init__(callable)

class abstractproperty

A decorator indicating abstract properties.

Deprecated, use ‘property’ with ‘abstractmethod’ instead:

class C(ABC):

@property @abstractmethod def my_abstract_property(self):

…

class ABCMeta

Metaclass for defining Abstract Base Classes (ABCs).

Use this metaclass to create an ABC. An ABC can be subclassed directly, and then acts as a mix-in class. You can also register unrelated concrete classes (even built-in classes) and unrelated ABCs as ‘virtual subclasses’ – these and their descendants will be considered subclasses of the registering ABC by the built-in issubclass() function, but the registering ABC won’t show up in their MRO (Method Resolution Order) nor will method implementations defined by the registering ABC be callable (not even via super()).

static __new__(mcls, name, bases, namespace, **kwargs)

register(subclass)

Register a virtual subclass of an ABC.

Returns the subclass, to allow usage as a class decorator.

__instancecheck__(instance)

Override for isinstance(instance, cls).

__subclasscheck__(subclass)

Override for issubclass(subclass, cls).

update_abstractmethods(cls)

Recalculate the set of abstract methods of an abstract class.

If a class has had one of its abstract methods implemented after the class was created, the method will not be considered implemented until this function is called. Alternatively, if a new abstract method has been added to the class, it will only be considered an abstract method of the class after this function is called.

This function should be called before any use is made of the class, usually in class decorators that add methods to the subject class.

Returns cls, to allow usage as a class decorator.

If cls is not an instance of ABCMeta, does nothing.

class ABC

Helper class that provides a standard way to create an ABC using inheritance.