finding name of instances created

Steven Bethard steven.bethard at
Fri Jan 21 21:46:40 EST 2005

André wrote:
> Steven Bethard wrote:
>>André wrote:
>>>Using the method suggested by Steven Bethard, I *almost* got it
> working
>>>the way I would like.
> [snip]
>>It looks like you want PrivateClass.dict updated every time that
>>globals() is updated.
> yes, that is what I would like to do.
>>You can just use globals directly instead:
>>py> class PrivateClass(object):
>>...     def __init__(self, globals):
>>...         self.globals = globals
>>...     def apparently_simple_method(self):
>>...         for name, value in self.globals.iteritems():
>>...             if value is self:
>>...                 print "instance %s called not so simple" % name
>>py> def public_class():
>>...     return PrivateClass(globals())
>>py> alpha = public_class()
>>py> alpha.apparently_simple_method()
>>instance alpha called not so simple
>>py> beta = public_class()
>>py> beta.apparently_simple_method()
>>instance beta called not so simple
> That's exactly what I was looking for; thank you!
>>On the other hand, the iteration in
>>PrivateClass.apparently_simple_method has a very bad code smell...
> I'm not sure what you mean...
> Is it because it makes use of information that is
> exterior to the class, which is not passed as a parameter
> to the method?
> [feel free to ignore this question if you want; you have
> already helped me tremendously!!!]

There's a couple things I don't like about it:

(1) Generally, I don't like passing globals() around.  It's probably 
okay in this scenario though because if you want to have the user code 
in a different module, you can do something like:
     def public_class():
         return PrivateClass(usermodule.__dict__)

(2) The really bad code smell however is having to iterate through all 
the values in globals to find the key you're looking for...  Especially 
when you have to check the type of each item...  In a perfect world, you 
would already have a PrivateClass->name mapping somewhere and this 
should be a simple dict lookup instead of an iterative search...  See my 
other post about potentially pre-processing your user input to see how 
you can convert the iteration to a simple attribute lookup.


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