Python @ property.setter [英] Python @property.setter

问题描述

创建装饰器的基本方法是

The basic way of creating decorators is

def my_decorator(f):
    def _f(*args, **kwargs):
        # do something using f
        pass
    return _f

@my_decorator
def f(...):
    ...

但是那样一来，您就无法定义装饰器，例如 @ property.setter ，因为属性的名称(以及装饰器的名称)每次都不同.

But that way you cannot define decorators like @property.setter, because the name of the property (and thus the name of the decorator) is different every time.

然后如何定义 @ property.setter ?可以在Python中做类似的事情吗，还是内置功能仅在C(实现)级别可用?

How is it @property.setter defined then? Is it possible to do something similar in Python, or is it built-in feature available only from C (implementation) level?

推荐答案

您正在寻找的是称为描述符:

 class Descriptor(object):
   def __get__(self, instance, _type=None):
     pass
   def __set__(self, obj, value):
     pass

您可以自由地实施自己认为合适的事情. property 装饰器只是一个描述符的实例(或多或少)，您可以在描述此项的文档中看到它们的实现方式.

You are free to implement things as you see fit. The property decorator is just an instance of a descriptor (more or less) and you can see how they'd implement it in the documents describing this item.

这是一个例子:

  class _Wrapper(object):
    def __init__(self, caller, instance):
      self.caller = caller
      self.instance = instance

    def __call__(self, *args, **kwargs):
      print "I've been wrapped!"
      return self.caller(self.instance, *args, **kwargs)

  class Accouncer(object):
    def __init__(self, method):
      self.method = method

    def __get__(self, instance, _type=None):
      return _Wrapper(self.method, instance)

  def vocal(func):
    return Accouncer(func)

  class Ha(object):
    @vocal
    def stuff(self):
      return 1

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