set and dict iteration

[Aaron Brady]

On Thursday, August 16, 2012 9:30:42 PM UTC-5, Paul Rubin wrote:
> Steven D'Aprano <steve+comp.lang.python at pearwood.info> writes:
> 
> > Luckily, Python is open source. If anyone thinks that sets and dicts 
> 
> > should include more code protecting against mutation-during-iteration, 
> 
> > they are more than welcome to come up with a patch. Don't forget unit and 
> 
> > regression tests, and also a set of timing results which show that the 
> 
> > slow-down isn't excessive.
> 
> 
> 
> It could be a debugging option, in which case even a fairly significant
> 
> slowdown is acceptable.

Another possibility is to use the 'gc.get_referrers' mechanism to obtain the iterators.


import gc
a= set( ( 0, 1, 2 ) )
b= iter( a )
c= iter( a )
d= iter( a )
print( gc.get_referrers( a ) )

Output:

[<set_iterator object at 0x00C0B9E0>, <set_iterator object at 0x00C0BA08>, <set_iterator object at 0x00C0BA30>, [others] ]

This approach wouldn't be as time-efficient as a dedicated secondary structure, due to the other objects which refer to the set, including variable namespaces.