Python: dereferencing weakproxy

Question

Is there any way to get the original object from a weakproxy pointed to it? eg is there the inverse to weakref.proxy()?

A simplified example(python2.7):

import weakref

class C(object):
    def __init__(self, other):
        self.other = weakref.proxy(other)

class Other(object):
    pass

others = [Other() for i in xrange(3)]

my_list = [C(others[i % len(others)]) for i in xrange(10)]

I need to get the list of unique other members from my_list. The way I prefer for such tasks is to use set:

unique_others = {x.other for x in my_list}

Unfortunately this throws TypeError: unhashable type: 'weakproxy'

I have managed to solve the specific problem in an imperative way(slow and dirty):

unique_others = []
for x in my_list:
    if x.other in unique_others:
        continue
    unique_others.append(x.other)

but the general problem noted in the caption is still active. What if I have only my_list under control and others are burried in some lib and someone may delete them at any time, and I want to prevent the deletion by collecting nonweak refs in a list?

Or I may want to get the repr() of the object itself, not <weakproxy at xx to Other at xx> I guess there should be something like weakref.unproxy I'm not aware about.

Answer 1

I know that this is an old question, but I've been bitten by it (so, there's no real 'unproxy' in the standard library) and wanted to share my solution...

The way I solved it to get the real instance was just creating a property which returned it (although I suggest using weakref.ref instead of a weakref.proxy as code should really check if it's still alive before accessing it instead of having to remember to catch an exception whenever any attribute is accessed).

Anyways, if you still must use a proxy, the code to get the real instance is:

import weakref

class MyClass(object):

    @property
    def real_self(self):
        return self

instance = MyClass()
proxied = weakref.proxy(instance)
assert proxied.real_self is instance