Python “装饰师的作用是什么？”；实现“迭代器”？

Werkzeug v0.11 我研究了Werkzeug的源代码，文件wsgi.py中的ClosingIterator类，由函数decorted实现\u迭代器：

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()
    """

我在文件_compat.py中找到了实现_迭代器的定义：

implements_iterator = _identity

_identity = lambda x: x

问题是:

---

实现迭代器的功能是什么？

Werkzeug同时针对Python2和Python3。如果在

compat.py

中向上滚动，您可以看到为Python 2定义了

implements\u迭代器

，如下所示：

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

这允许一个类实现一个方法（仅在Python2中调用），并在不做任何修改的情况下同时适用于Python2和Python3