Jython 2.1 __getattr__

发布于 2024-08-11 16:48:40 字数 1162 浏览 14 评论 0原文

我正在尝试在 jython v2.1 中为 java 对象(baseClient)实现包装器/代理类。一切似乎都工作正常,除非遇到以下语句:

if __client != None # __client is an instance of the ClientProxy class

__getattr__() 中调用 raise AttributeError(attr),因为 self.__baseClient > 没有 __ne__ 属性。 值得一提的是,我无法升级,因为 jython 是系统的一部分。有办法解决这个问题吗?

class ClientProxy:
    def __init__(self, baseClient):
        self.__baseClient = baseClient
        self.__initialised = 1

    def __getattr__(self, attr):
        if not self.__dict__.has_key('_ClientProxy__initialised'):
            raise AttributeError(attr)
        else:
            if hasattr(self.__baseClient, attr):
                return getattr(self.__baseClient, attr)
            else:
                raise AttributeError(attr)


    def __setattr__(self, attr, val):
        if not self.__dict__.has_key('_ClientProxy__initialised'):
            self.__dict__[attr] = val
            return

        if hasattr(self.__baseClient, attr):
            self.__baseClient.__setattr__(attr, val)
        else:
            self.__dict__[attr] = val

多谢!

I am trying to implement a wrapper/proxy class for a java object (baseClient) in jython v2.1. Everything seems to be working ok except when the following statement is encountered:

if __client != None # __client is an instance of the ClientProxy class

raise AttributeError(attr) is called in __getattr__(), because self.__baseClient doesn't have __ne__ attribute.
It's important to mention that I cannot upgrade because jython is a part of a system. Is there a way to get around this issue?

class ClientProxy:
    def __init__(self, baseClient):
        self.__baseClient = baseClient
        self.__initialised = 1

    def __getattr__(self, attr):
        if not self.__dict__.has_key('_ClientProxy__initialised'):
            raise AttributeError(attr)
        else:
            if hasattr(self.__baseClient, attr):
                return getattr(self.__baseClient, attr)
            else:
                raise AttributeError(attr)


    def __setattr__(self, attr, val):
        if not self.__dict__.has_key('_ClientProxy__initialised'):
            self.__dict__[attr] = val
            return

        if hasattr(self.__baseClient, attr):
            self.__baseClient.__setattr__(attr, val)
        else:
            self.__dict__[attr] = val

Thanks a lot!

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魂牵梦绕锁你心扉 2024-08-18 16:48:40
if __client != None:

为了针对特定实例(例如 None)进行测试,通常使用恒等运算符:

if __client is not None:

这将避免调用比较器的问题。

然而,事实上 __getattr__ 引发 AttributeError 应该不是问题。比较器应该推测性地调用 getattr 来获取 __cmp__ (在较新的 Python 上首先调用 __ne__),并且如果它得到一个 AttributeError它应该默默地吞掉它,然后退回到身份比较。为什么 AttributeError 在您的案例中会导致问题?

if __client != None:

For testing against specific instances such as None, it's idiomatic to use the identity operator:

if __client is not None:

This will avoid the problem of calling comparators.

However, the fact that __getattr__ raises AttributeError should not be a problem. The comparator should call getattr speculatively for __cmp__ (__ne__ first on newer Pythons), and if it gets an AttributeError it is supposed to silently swallow it and fall back to identity comparison instead. Why does the AttributeError cause a problem in your case?

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