Question

Given the following:

class MyClass:
    def __init__(self, someval):
        self.someval = someval
    def get_a_function(self):
        def result():
            return self.someval
        return result

inst = MyClass("my value")
func = inst.get_a_function()

I have only func, and would like to get inst. Is that possible, and if so, how? Note: I do not control MyClass or how inst is declared.

P.S. I know this is baaadddd style, but am curious if it can be done.

Answer 1

You notice how result returns self.someval, meaning that it has a closure. All you need to do is to dive into that closure. To do that, use the func_closure attribute:

>>> class MyClass:
...     def __init__(self, someval):
...         self.someval = someval
...     def get_a_function(self):
...         def result():
...             return self.someval
...         return result
... 
>>> inst = MyClass("my value")
>>> func = inst.get_a_function()
>>> func
<function result at 0x8d3efb4>
>>> func.func_closure
(<cell at 0x8dbc554: instance object at 0x8d321cc>,)
>>> func.func_closure[0].cell_contents
<__main__.MyClass instance at 0x8d321cc>

Note that I am just accessing the first element of the closure. If the function is more complicated, it may have multiple objects in its closure, and you need to test for which one you want.

Edit: This is really bad style btw 🙂