It seems that both the languages that I use regularly, Java and Python have issues with string concatenation. In both languages, the thing that seems to be the obvious way to concatenate strings is also the low performance way. There's so much string handling going on in the world that I just don't understand why strings are so broken this way. Seems like there hasn't been a lot of attention paid to strings, and probably only C++ programmers are aware of Hans J. Boehm's work on Ropes.

I was happy to find that for loops are not as fast as using map, but disappointed because list comprehensions are syntactic sugar for for loops and therefore also slow.

I was also surprised to find out that import statements are executed, although I guess if I had thought about it for a minute I would have realized that. Same for using calls like string.upper.

At least I'm on the way to building a mental model of performance for Python.