Why you are using _ and __ instead of just names of variables? For me it is harder to read if I use _ more in one line. Btw nice solution I took same approach, but using just def without lambda.

I think if you can avoid division, you should, because if not, I think, that you should handle Zero Division Error.

Why would that be necessary? Task states, that you're given words and you don't need to sanitize them. There are 100+ more unnecessary things he could do, what's the point of mentioning them?

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