python 定义类时在python中设置具有给定名称的类属性
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Setting a class attribute with a given name in python while defining the class
提问by prismofeverything
I am trying to do something like this:
我正在尝试做这样的事情：
property = 'name'
value = Thing()
class A:
setattr(A, property, value)
other_thing = 'normal attribute'
def __init__(self, etc)
#etc..........
But I can't seem to find the reference to the class to get the setattrto work the same as just assigning a variable in the class definition. How can I do this?
但我似乎无法找到对类的引用，setattr以使其与仅在类定义中分配变量一样工作。我怎样才能做到这一点？
采纳答案by Ignacio Vazquez-Abrams
You'll need to use a metaclass for this:
您需要为此使用元类：
property = 'foo'
value = 'bar'
class MC(type):
def __init__(cls, name, bases, dict):
setattr(cls, property, value)
super(MC, cls).__init__(name, bases, dict)
class C(object):
__metaclass__ = MC
print C.foo
回答by Vitalik Verhovodov
You can do it even simpler:
你可以做得更简单：
class A():
vars()['key'] = 'value'
In contrast to the previous answer, this solution plays well with external metaclasses (for ex., Django models).
与之前的答案相反，此解决方案适用于外部元类（例如，Django 模型）。
回答by keturn
This may be because the class Ais not fully initialized when you do your setattr(A, p, v)there.
这可能是因为A当你在setattr(A, p, v)那里做你的时候这个类没有完全初始化。
The first thing to try would be to just move the settattr down to after you close the classblock and see if that works, e.g.
首先要尝试的是在关闭class块后将 settattr 向下移动，看看是否有效，例如
class A(object):
pass
setattr(A, property, value)
Otherwise, that thing Ignacio just said about metaclasses.
回答by StoneyD
So I know this is really old and probably beating a dead horse and this may not have been possible at the time but I cam across this trying to solve my own problem.
所以我知道这真的很旧，可能会打败一匹死马，这在当时可能是不可能的，但我遇到了这个试图解决我自己的问题。
I realized this can be accomplished without metaclassing.
我意识到这可以在没有元类的情况下完成。
The setattr takes and object, accessor name, and value. Well the object is not the class name it's the specific instance of the class, which can be accomplished with self.
setattr 接受对象、访问器名称和值。那么对象不是类名，它是类的特定实例，这可以通过 self 来完成。
class A(object):
def __init__(self):
self.a = 'i am a accessor'
setattr(self, 'key', 'value')
a = A()
print a.a
print a.key
