plain-abc
Another ABC implementation without metaclass.
It is a little bit annoying to have metaclass conflict,
especially when trying to use ABC along with other libraries.
plain-abc provides a simple ABC implementation without metaclass.
Installation
pip install plain-abcUsage
But you can also use plain-abc to solve the problem:
from abc import abstractmethod
from plain_abc import PlainABC
class _SomeHiddenMetaclass(type):
pass
class Base(metaclass=_SomeHiddenMetaclass):
pass
class IFoo(PlainABC):
@abstractmethod
def foo(self): ...
class Foo(Base, IFoo):
def foo(self): ...To extend an abstract class as another abstract class,
PlainABC is required to be one of the bases:
from abc import abstractmethod
from plain_abc import PlainABC
class IEntity(PlainABC):
@abstractmethod
def get_id(self) -> str: ...
class IProjectile(IEntity, PlainABC):
@abstractmethod
def get_speed(self) -> float: ...
class Arrow(IProjectile):
def get_id(self) -> str: ...
def get_speed(self) -> float: ...To skip signature checking,
you can add the member names in __abc_concrete_members__ of a subclass:
from abc import abstractmethod
from enum import Enum
from plain_abc import PlainABC
class IEnum(PlainABC):
@property
@abstractmethod
def foo(self) -> str:
...
class Foo(IEnum, Enum):
# for python 3.10 or lower
__abc_concrete_members__ = ('foo',)
foo = 'foo'
assert Foo.foo.value == 'foo'
To solve metaclass conflict without plain-abc
Here is an example of metaclass conflict
and how to mix ABCMeta with other metaclasses.
from abc import ABC, ABCMeta, abstractmethod
class _SomeHiddenMetaclass(type):
...
class Base(metaclass=_SomeHiddenMetaclass):
...
class IFoo(ABC):
@abstractmethod
def foo(self): ...
# oh no, metaclass conflict!
# class Foo(Base, IFoo):
# def foo(self): ...
# create a new metaclass to solve the conflict
class NewMetaclass(_SomeHiddenMetaclass, ABCMeta):
...
class Foo(Base, IFoo, metaclass=NewMetaclass):
def foo(self): ...
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