This is a fun benchmark in C++, where you can see that GCC has a more restrictive small string optimization. On my desktop the main python example runs in 3.1s. Then this code

    void example() {
      for (int64_t i = 1; i <= 20; ++i) {
        for (int64_t j = 1; j <= 1'000'000; ++j) {
          std::to_string(j);
        }
      }
    }

runs with GCC in 2.0s and with clang in 133ms, so 15x faster.

I've also benchmarked it in Julia:

    function example()
      for j = 1:20, i = 1:1_000_000
        string(i)
      end
    end

which runs in 592ms. Julia has no small string optimization and does have proper unicode support by default.

None of the compilers can see that the loop can be optimized out.