abstractmethod没有定义

Question

我无法运行此代码,因为我得到了异常:

NameError: name 'abstractmethod' is not defined
File "C:\Tests\trunk\PythonTests\AbstractClasses.py", line 12, in <module>
  class MyIterable:
File "C:\Tests\trunk\PythonTests\AbstractClasses.py", line 15, in MyIterable
  @abstractmethod

from abc import ABCMeta

class Foo(object):
    def __getitem__(self, index):
        print '__get_item__ Foo'
    def __len__(self):
        print '__len__ Foo'
    def get_iterator(self):
        print 'get_iterator Foo'
        return iter(self)

class MyIterable:
    __metaclass__ = ABCMeta

    @abstractmethod
    def __iter__(self):
        while False:
            yield None

    def get_iterator(self):
        return self.__iter__()

    @classmethod
    def __subclasshook__(cls, C):
        if cls is MyIterable:
            if any("__iter__" in B.__dict__ for B in C.__mro__):
                print "I'm in __subclasshook__"
                return True
        return NotImplemented

MyIterable.register(Foo)

x=Foo()
x.__subclasshook__()

我确信代码没问题,因为我是从http://docs.python.org/library/abc.html获得的

编辑

谢谢你的回答,它现在有效,但为什么呢

print '__subclasshook__'

这不起作用？我没有进入Debug I/0

Answer 1

你只导入了 ABCMeta

from abc import ABCMeta

也导入 abstractmethod

from abc import ABCMeta, abstractmethod

一切都应该没问题.

Answer 2

您需要abstractmethod从导入abc。是抽象基类abc的内置 Python 包。

一个例子：

from abc import abstractmethod

class Foo:
    def __init():
        pass
    
    @abstractmethod
    def bar():
        pass