The thing though is it's a bad requirement. There are any number of great candidates who could be proficient in Python - the skills are very transferrable. (It's like trying to find a painter and filtering out people who have never painted a brown houses)
The thing you're screening for by being so specific is not finding the most qualified person, you're going to end up with the person with the most time and patience to fib or lie on their resume.
> I doubt the "best candidate" is also the person who can't be bothered to take 10 minutes to update their resume before pressing submit.
That's exactly wrong - the best candidates are going to be busy people who are great at their job - the people jumping through HR hoops to get hired are by nature going to be worse candidates.