> On Thu, Jan 7, 2016 at 11:14 AM, Joseph Fox-Rabinovitz
> wrote:
>
> Hi,
>
> I have a module attribute whose name starts with a pair of underscores. I am
> apparently unable to access it directly in a class method (within the same
> module, but that is not relevant as far as I can tell). The following bit of
> code illustrates the situation:
>
> __a = 3
> class B:
> def __init__(self):
> global __a
> self.a = __a
> b = B()
>
> This results in a NameError because of name-mangling, despite the global
> declaration:
>
> Traceback (most recent call last):
> File "", line 1, in
> File "", line 4, in __init__
> NameError: name '_B__a' is not defined
>
> Not using global does not make a difference. I posted a similar question on
> Stack Overflow, where the only reasonable answer given was to wrap __a in a
> container whose name is not mangled. For example, doing `self.a =
> globals()['__a']` or manually creating a dictionary with a non-mangled name
> and accessing that.
>
> I feel that there should be some way of accessing __a within the class
> directly in Python 3. Clearly my expectation that global would fix the issue
> is incorrect. I would appreciate either a solution or an explanation of what
> is going on that would convince me that accessing a module attribute in such
> a way should be forbidden.
>
> -Joseph Fox-Rabinovitz
>
> P.S. For reference, the Stack Overflow question is here:
> http://stackoverflow.com/questions/34621484/how-to-access-private-variable-of-python-module-from-class
One more detail that makes me think that name mangling may be getting
greedy to the point of bugginess:
__a = 3
class B:
def __init__(self):
m = sys.modules[__name__]
self.a = m.__a
b = B()
Raises the same exception as all the other way I tried to access __a:
'module' object has no attribute '_B__a'!
-Joseph
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