Python 3 vs Python 2.7

Question

How fast is Python 3.x compared to Python 2.7?

Answer 1

Python 3 might have some utilities to deal with some problems faster than Python 2, or Python 2 may be better optimized because it is more mature. 

If you were to benchmark a large Python 2 codebase on a JIT engine against a large Python 3 codebase on a raw interpreter, Python 2 would probably win if it has a decent JIT compiler.