有什么方法可以获得Cython的“接口”吗？(Any way to get “interfaces” with Cython?)

有什么方法可以获得Cython的“接口”吗？(Any way to get “interfaces” with Cython?)

我的应用程序需要有几个从单个基类继承的Cython cdef类，但仍然实现了许多接口。 这些接口将用于对类进行isinstance()检查，以确保它们符合某些接口。

我知道Cython不支持多重继承，但是有任何方法可以实现类似接口的行为。 这似乎是Cython的一个相当明显的限制，我确信我不是唯一遇到这个问题的人。

My application needs to have several Cython cdef classes that inherit from a single base class, but yet still implement many interfaces. These interfaces would be used to do isinstance() checks on the classes to make sure they conform to certain interfaces.

I know Cython doesn't support multiple inheritance, but is there any way at all to implement interface-like behavior. It seems like a rather glaring limitation in Cython and I'm sure I'm not the only person to encounter this problem.

最满意答案

当你面对一个你无法改变但你想要与一个接口关联的基类时，你就像在纯Python中那样完全这样做：你使用抽象基类模块

有两种选择可供选择：

你要么把你的类register为属于一个接口（“抽象基类”），就像我为InterfaceA做的那样，或者 你给你的接口一个__subclasshook__ ，它允许它使用正确的方法来声明任何类，就像我为InterfaceB所做的那样。

例：

import abc # define the interfaces as normal (non-Cython) Python classes class InterfaceA(metaclass=abc.ABCMeta): # Python3 syntax. metaclasses are slightly different in python2 pass class InterfaceB(metaclass=abc.ABCMeta): @abc.abstractmethod def useful_function(self): raise NotImplementedError() @classmethod def __subclasshook__(cls,other_cls): if cls is InterfaceB: if any("useful_function" in B.__dict__ for B in C.__mro__): return True return NotImplemented # our Cython class cdef class C: def useful_function(self): return 1 c = C() print(isinstance(c,InterfaceA)) # prints False InterfaceA.register(C) print(isinstance(c,InterfaceA)) # prints True print(isinstance(c,InterfaceB)) # prints True

You do it exactly as you would in pure Python when faced with a base class that you can't change but that you want to associate with an interface: you use the abstract base classes module

There's two options to chose from:

you either register your class as belonging to an interface ("abstract base class") like I've done for InterfaceA, or you give your interface a __subclasshook__ that allows it to claim any class with the right methods like I've done for InterfaceB.

Example:

import abc # define the interfaces as normal (non-Cython) Python classes class InterfaceA(metaclass=abc.ABCMeta): # Python3 syntax. metaclasses are slightly different in python2 pass class InterfaceB(metaclass=abc.ABCMeta): @abc.abstractmethod def useful_function(self): raise NotImplementedError() @classmethod def __subclasshook__(cls,other_cls): if cls is InterfaceB: if any("useful_function" in B.__dict__ for B in C.__mro__): return True return NotImplemented # our Cython class cdef class C: def useful_function(self): return 1 c = C() print(isinstance(c,InterfaceA)) # prints False InterfaceA.register(C) print(isinstance(c,InterfaceA)) # prints True print(isinstance(c,InterfaceB)) # prints True