Help with sets

Terry Reedy tjreedy at
Tue Oct 5 22:45:40 CEST 2010

On 10/5/2010 3:01 AM, Ian Kelly wrote:

> self._pos = {predicate: {object: {subject: None}}}
> That's a bit ugly because the None serves no purpose here; the value
> associated with the subject has no meaning in this context.

This is what we did in Python before sets were added.

 >  It also
> uselessly takes up space in memory that could add up to significant
> wastage if the data structure grows to be large.
> The other major difference between dicts and sets is that sets provide
> mathematical operations such as intersection and difference that dicts
> do not, but that doesn't appear to be relevant in this context.

These two reasons are why we added sets.

Terry Jan Reedy

More information about the Python-list mailing list