[Pythonmac-SIG] Sets and Speed

[Bob Ippolito]

On May 30, 2005, at 2:48 PM, Yair Benita wrote:

> I usually combine 2 sets using union but one set is much smaller  
> than the other. It is better to do it using "add", as suggested,  
> and that is my solution. I didn't realize that using "add" will not  
> create redundancy, as you said these are like keys in a dictionary  
> so no duplicates can occur. I suppose "union" is worth doing when I  
> have two big sets to be combined.

Union is for combining two sets and creating a third set -- which  
involves a lot of copying and reference counting.  If you want to  
combine two sets, simply mutating one, use update.

-bob