It's odd many coders are rooting for a particular language without even asking: Most productive for what? And how do you measure that productivity?
I think this has been said many times, but its worth hammering it home.
Python, yes its productive for many things; useless if you are creating an O/S in which its probably less productive.
I think the more libraries that a particular language has, generally the more productive it is (assuming like python the modules intergrate nicely, unlike say perl.)
Also I find people mistake speed for productivity as well. What's the point of writing 10 components in a day, if all 10 are useless, or to slow. Sometimes you need spend time on the core code and make sure that's correct.