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Date: Sat, 8 Sep 2012 08:42:56 -0700 (PDT)
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Subject: Re: set and dict iteration
From: Aaron Brady <castironpi@gmail.com>
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Xref: csiph.com comp.lang.python:28726

On Monday, September 3, 2012 8:59:16 PM UTC-5, Steven D'Aprano wrote:
> On Mon, 03 Sep 2012 21:50:57 -0400, Dave Angel wrote:
> 
> 
> 
> > On 09/03/2012 09:26 PM, Steven D'Aprano wrote:
> 
> 
> 
> >> An unsigned C int can count up to 4,294,967,295. I propose that you say
> 
> >> that is enough iterators for anyone, and use a single, simple, version
> 
> >> counter in the dict and the iterator. If somebody exceeds that many
> 
> >> iterators to a single dict or set,
> 
> > 
> 
> > I think you have the count confused.  it has to be a count of how many
> 
> > changes have been made to the dict or set, not how many iterators exist.
> 
> 
> 
> Oops, yes you are absolutely right. It's a version number, not a count of 
> 
> iterators.
> 
> 
> 
> 
> 
> -- 
> 
> Steven

Hello.  We have a number of proposed solutions so far.

1) Collection of iterators
  a) Linked list
    i) Uncounted references
    ii) Counted references
    iii) Weak references
  b) Weak set
2) Serial index / timestamp
  a) No overflow - Python longs
  b) Overflow - C ints / shorts / chars
  c) Reset index if no iterators left
3) Iterator count
  - Raise exception on set modifications, not iteration

Note, "2b" still leaves the possibility of missing a case and letting an error pass silently, as the current behavior does.  The rest catch the error 100% of the time.

Anyway, I plan to develop the above patch for the 'dict' class.  Would anyone like to take over or help me do it?