I don't agree with @dalkon here on the use of string.format. Sure, it can be used if you have to concatenate a lot of things (as in the same statement and not concatenating 1 thing multiple times in a loop) to improve readability, but don't use it everywhere. Concatenating strings with ".." is fine. I'm actually curious about the performance difference between using two dots to concatenate a string vs string.format, if there really is a huge difference then sure we should consider using string.format, but if there isn't, then please don't use it unless you are constructing a string from lots of variables that makes it harder to follow when using "..".