I've updated the kata and you can select 3.6 now, your code works there.

Online I see "Error code 136 - Erroneous Arithmetic Operation", which fits with what I think went wrong.

Walk through your code with a string that's one letter long, like "a"

If you can use "markup" to presere your code's intentation, it will be much easier to read.

You're making some assumptions about floating point numbers that may or may not be true for this problem.
For example, do you expect the following expression to evaluate to true?
.1 * 3 == .3

It isn't true in both Python 2.x and Python 3.x.

Using & operator with two sets creates a new set containing the elements present in both sets.

https://docs.python.org/3/library/stdtypes.html#set for more infos. :)

You're not using the same Python version, and there are differences between them. When posting code like that, mark your post as having spoiler content.