装饰器“implements_iterator”的功能是什么？

Question

WERKZEUG v0.11 我stduy WERKZEUG的源代码，文件wsgi.py类ClosingIterator，按功能implements_iterator decorted：

wsgi.py

@implements_iterator 
class ClosingIterator(object): 

    """The WSGI specification requires that all middlewares and gateways 
    respect the `close` callback of an iterator. Because it is useful to add 
    another close action to a returned iterator and adding a custom iterator 
    is a boring task this class can be used for that:: 

     return ClosingIterator(app(environ, start_response), [cleanup_session, 
                   cleanup_locals]) 

    If there is just one close function it can be passed instead of the list. 

    A closing iterator is not needed if the application uses response objects 
    and finishes the processing if the response is started:: 

     try: 
      return response(environ, start_response) 
     finally: 
      cleanup_session() 
      cleanup_locals() 
    """ 

我发现implements_iterator中的定义文件_compat.py：

implements_iterator = _identity 

_identity = lambda x: x 

的问题是： 是什么implements_iterator的功能？

Answer 1

WERKZEUG目标两者的Python 2和Python 3，如果您在compat.py向上滚动，你可以看到implements_iterator是为Python 2定义如下：

def implements_iterator(cls): 
    cls.next = cls.__next__ 
    del cls.__next__ 
    return cls 

这样一个类来实现一个__next__方法（在Python 2中称为next），并且无需任何修改即可用于Python 2和Python 3。