Regarding the actual questions, I just like to talk about the actual CV / past. There's got to be something exciting in their previous job. Or outside of job. Or during studies. If there isn't... depends if you look for someone with creative solutions, or you're ok with average coder to type out standard CRUD.

Otherwise, I really like small tasks without limits. For python job it was something like "read csv, write to database". It can be a 3-liner and take 10 minutes. But if you say "no limits, make it production quality code", there's so much you can learn about the candidate.

It can have error reporting. It can have documentation. It can be a proper module. It can handle encoding issues correctly. It can care about SQL injection or not. It can have configurable paths and backends. It can support py2/py3/both.