It's all been said, but a couple notes: I also teach beginners Python -- and I absolutely teach them to use "is None" (I'd have to look at my notes, but I think around lesson 3), In fact, I also teach about what ``is`` means, and how it is very different from ``==``. I have seen all too many instances of code like: if c is 0: ... Which actually DOES work, for small integers, on cPython -- but it is a very bad idea. (though I think it raises a Warning now) And your students are almost guaranteed to encounter an occasion where using == None causes problems at some point in their programming careers -- much better to be aware of it early on! As others have said, there is no such thing as "mandatory" for PEP 8. It is a "style" guide. Though interestingly, the recommendation of using is with None is not just one of style, there is a real semantic difference. In fact, of all the things in PEP 8, this might actually be one of the more important! I encourage you NOT to turn it off in your students' linter. -CHB -- Christopher Barker, PhD (Chris) Python Language Consulting - Teaching - Scientific Software Development - Desktop GUI and Web Development - wxPython, numpy, scipy, Cython