Cycle detection and object memory usage?

[Jim Kleckner]

Gabriel Genellina wrote:
> En Sun, 20 May 2007 23:54:15 -0300, Jim Kleckner <jek-gmane at kleckner.net>  
> escribió:
> 
>> I understand from the documentation that types with a finalizer method
>> that participate in cycles can't be collected.
> 
> Yes; older Python versions could not manage any kind of cycles, now only  
> objects with __del__ cause problems.
> You can explicitely break the cycle (removing the reference, ensuring that  
> some finalization method is always called, maybe using try/finally) or you  
> may use weak references (by example, in a tree-like structure, a node  
> might hold a weak reference to its parent).
> 
>> What is the best way to go about finding these cycles?
>> Googling gives a variety of methods none of which seem terribly
>> mainstream for such a common problem.
> 
> Avoid them in the first place :)
> Use the gc module: after a call to gc.collect(), see if something remains  
> in gc.garbage

I would have sworn that there were uncollectable objects when I
tried this before.  Now they don't show up.  I guess that is good...
Which leads to

>> Object memory usage:
>>
>> Has anyone written a function to sweep out an object to discover how
>> much memory it and all the objects it references is using?  This would
>> be great for performance tuning.
> 
> A rough estimate may be the object's pickle size. But it's hard to measure  
> precisely; by example, strings are immutable and you may have thousands of  
> shared references to the same string, and they require just a few bytes  
> each.

Good idea, thanks.

I take it then that memory profiling isn't available?