Nested inner classes and inheritance -> namespace problem

Wed Apr 13 06:08:21 EDT 2011

Larry Hastings wrote:
>> The problem: if you're currently in a nested class, you can't look up 
> variables in the outer "class scope".
>> For example, this code fails in Python 3:
>> class Outer:
> class Inner:
> class Worker:
> pass
>> class InnerSubclass(Inner):
> class Worker(Inner.Worker):
> pass
>> It fails at the definition of Worker inside InnerSubclass. Python 3 
> can't find "Inner", in order to get to "Inner.Worker".
>> Adding "global Inner" just above that line doesn't help--it's not a 
> global.
> Adding "nonlocal Inner" just above that line doesn't help either--I 
> suppose it's the /wrong kind/ of nonlocal. nonlocal is for nested 
> functions, and this uses nested classes.
>> You can tell me YAGNI, but I tripped over this because I wanted it. 
> It's not a contrived example. I actually use inner classes a lot; I 
> suppose I'm relatively alone in doing so.
>> Yes, I could make the problem go away if I didn't have nested inner 
> classes like this. But I like this structure. Any idea how I can 
> make it work while preserving the nesting and inheritance?
>> Thanks,
>>> /larry/
class Outer:
 class Inner:
 class Worker:
 pass
 print 'Outer ', locals()
 class InnerSubclass(Inner):
 print 'InnerSubclass', locals()
 class Worker:
 pass
Outer {'__module__': '__main__', 'Inner': <class __main__.Inner at 
0x963a7ac>}
InnerSubclass {'__module__': '__main__'}
I use myself nested classes a lot, but only as namespace / enum, meaning 
there is no inheritance involved. I don't think that you can do what you 
are trying to do.
Outer would actually be a module, not a class.
JM