Using double underscores makes the variable unusable outside the class.

Why insert at beginning? You dont have to reverse the list anymore but every other action gets less efficient. (pop last vs pop intermediate; insert vs append)

It's shorter, meaningful and fast, so I consider it a good practice.

I had no idea! That's really neat.

Would you consider the str.translate function py3 with it's added requirement (assuming from comments above) would be 'best practice'?

Amazing!

I would also be interesting in seeing a test in which this solution fails.

Sorry, I misunderstood.
This translation is rather old and I am not the Python translator.
Moreover - as you might know - when more than 500 warriors have passed a kata in a given language it is not authorized to change the tests. Some months ago I added some tests in a few other languages, in Python it was impossible.
Anyway thanks for your posts.

[JAVA]
I can pass all cases except case 4, which length of int[] a and int[] b both 0. i've already checked for this situation at the first time as the code:

if(a.length == 0 || b.length == 0){
return false;
}

but it didn't work!!
isn't it right? did i miss something?

It is not because your solution is not the good one that the tests are broken.
920 guys passed the Python kata and I just tied a few solutions, all worked fine.
To post an issue you should at least given the output of a failed test...

I don't really remember why I chose those names, it was really long ago :)
However, I did a fork on this back then, where "count" is actually absent, check this out:
https://www.codewars.com/kumite/5572e7805a417acd480000f3?sel=5572e992b52d506aa50001dd