Thanks for the tips. As I mentioned, I am kicking the tires with Nim to see how it behaves. My goal isn't to find the fastest way to create a 100M string containing all x's in either Python or Nim, but rather for me to get a feel for how one behaves vs the other. If I run stupid tests like these and they all come out great with Nim, fantastic! That gives me a lot of confidence in it. If I get unexpected results, I'd like to understand why.
I have a 200K line Python 2.7 app. When I have run small tests comparing Python 2 vs 3, Python 2 is often 50% faster (I don't need or want Unicode). Maybe if the whole app was running in Py3 it would overall be faster, but based on what I've seen, that seems uncertain. So for my particular situation, I don't care how Nim compares to Py3. For grins, I ran the s = s + 'x' string test on Python2 and Python3.6.8 (all I have), and Py3 was 44% slower.
