[Tutor] Creating a two dimension set

[Phil]

I now have access to the Internet again and I thank everyone for their 
advice.

I have now solved the error that I had with a particular Sudoku example. 
It turned out to be an error that only showed itself under certain 
conditions. Not having meaningful function names (the function names are 
still not ideal) and not understanding my own overly complex code that I 
wrote a few years ago was really the cause of my confusion and had 
nothing to do with the use of sets. I don't think that there is any 
advantage in the use of a set of candidates over a list of candidates 
and I think that I'll return to the list method once I get through the 
100s of e-mails that I've just downloaded.

If nothing else, programming keeps me occupied.

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Regards,
Phil