子类化 Python 的 `property` [英] Subclassing Python's `property`
问题描述
在我的一个类中,我有许多属性在获取和设置方面做非常相似的事情.所以我将 property
的参数抽象成一个工厂函数:
In one of my classes, I have a number of properties that do very similar things on getting and setting. So I abstracted the arguments to property
into a factory function:
def property_args(name):
def getter(self):
# do something
return getattr(self, '_' + name)
def setter(self, value)
# do something
setattr(self, '_' + name, value)
return getter, setter
class MyClass(object):
def __init__(self):
self._x = None
x = property(*property_args('x')) # obviously there's more than one of these IRL
然而,我后来发现 property
实际上是一个类,将它子类化将是完美的选择.我在文档中找不到任何解释我需要覆盖的内容(以及 __init__
等的参数签名),而且我真的不想去寻找 C 源代码为了它.有谁知道我在哪里可以找到这些信息?
However, I've since discovered that property
is in fact a class, and subclassing it would be perfect for this. I can't find anything in the documentation that explains what I need to override (and the argument signatures of __init__
etc), and I don't really want to have to go hunting in the C source code for it. Does anyone know where I can find this information?
推荐答案
以下是 property() 中代码的纯 Python 等效项:
Here is a pure Python equivalent for the code in property():
class Property(object):
"Emulate PyProperty_Type() in Objects/descrobject.c"
def __init__(self, fget=None, fset=None, fdel=None, doc=None):
self.fget = fget
self.fset = fset
self.fdel = fdel
if doc is None and fget is not None:
doc = fget.__doc__
self.__doc__ = doc
def __get__(self, obj, objtype=None):
if obj is None:
return self
if self.fget is None:
raise AttributeError("unreadable attribute")
return self.fget(obj)
def __set__(self, obj, value):
if self.fset is None:
raise AttributeError("can't set attribute")
self.fset(obj, value)
def __delete__(self, obj):
if self.fdel is None:
raise AttributeError("can't delete attribute")
self.fdel(obj)
def getter(self, fget):
return type(self)(fget, self.fset, self.fdel, self.__doc__)
def setter(self, fset):
return type(self)(self.fget, fset, self.fdel, self.__doc__)
def deleter(self, fdel):
return type(self)(self.fget, self.fset, fdel, self.__doc__)
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