[commandlinefan]

Well... try not to take this personally, but... that means that you're not really an expert in Python, which is what (I assume) the interviewer in the linked post was looking for. You're capable in several languages, and may be an expert in one or more of them, but if they're looking for Python expertise, asking you how to find the length of a string is a good way to get a feel for how much time you're going to need to get to where you can really be trusted to produce mission-critical Python software (which may not be a deal breaker, if you're good at a lot of other things).