防止 Python 中类方法的重写属性？

发布于 2024-11-28 10:39:34 字数 668 浏览 4 评论 0原文

我有以下代码：

class Test(object):

    _spam = 42

    @classmethod
    def get_spam(cls):
        cls._spam

    @classmethod
    def set_spam(cls, value):
        cls._spam = value

    spam = property(get_spam, set_spam)

print Test.spam
Test.spam = 24
print Test.spam

输出是：

<property object at 0x01E55BD0>
24

有什么方法可以防止 Test.spam 的设置覆盖该属性吗？我不想使用 Test.spam 来设置 Test._spam 的值。 setter 和 getter 必须保留为类方法，并且我不想调用 Test.set_spam。

输出应该是：

<property object at 0x01E55BD0>
<property object at 0x01E55BD0>

原文

I have the following code:

class Test(object):

    _spam = 42

    @classmethod
    def get_spam(cls):
        cls._spam

    @classmethod
    def set_spam(cls, value):
        cls._spam = value

    spam = property(get_spam, set_spam)

print Test.spam
Test.spam = 24
print Test.spam

The output is:

<property object at 0x01E55BD0>
24

Is there any way to prevent the setting of Test.spam from overriding the property? I don't want to use Test.spam to set the value of Test._spam. The setter and getter have to remain as class methods, and I do not want to have to call Test.set_spam.

The output should be:

<property object at 0x01E55BD0>
<property object at 0x01E55BD0>

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爱格式化 2024-12-05 10:39:34

我想这可以防止开发人员意外覆盖 Test 的垃圾邮件属性。这就是你想要这个的原因吗？我不确定这是一个好主意（如果开发人员想要覆盖垃圾邮件属性怎么办？为什么要设置障碍？），但是......

您可以使用元类。如果您没有为元类的属性提供 setter，则 Test.spam 将引发 AttributeError:

class MetaTest(type):
    @property
    def spam(cls):
        return cls._spam

class Test(object):
    __metaclass__=MetaTest
    _spam = 42

    @classmethod
    def get_spam(cls):
        cls._spam

    @classmethod
    def set_spam(cls, value):
        cls._spam = value

    spam = property(get_spam, set_spam)

print Test.spam
# 42

But

Test.spam = 24

raises

AttributeError: can't set attribute

I suppose this stops developers from accidentally overwriting Test's spam property. Is that why you want this? I not sure that is a good idea (what if a developer wants to override the spam property? why throw up roadblocks?), but...

You could use a metaclass. If you don't supply a setter for the metaclass's property, then Test.spam will raise an AttributeError:

class MetaTest(type):
    @property
    def spam(cls):
        return cls._spam

class Test(object):
    __metaclass__=MetaTest
    _spam = 42

    @classmethod
    def get_spam(cls):
        cls._spam

    @classmethod
    def set_spam(cls, value):
        cls._spam = value

    spam = property(get_spam, set_spam)

print Test.spam
# 42

But