I'm a PhD student and use Python to write the code I use for my research.  My workflow often consists of making a small change to the code, running the program, seeing whether the results  improved, and repeating the process.  Because of this, I find myself spending more time waiting for my program to run than I do actually working on it (a common experience, I know).  I'm currently using the most recent version of Python 2 on my system, so my question is whether switching to Python 3 is going to give me any speed boost or not.  At this point, I don't really have a compelling reason to move to Python 3, so if the execution speeds are similar, I'll probably just stick with 2.x.  I know I'm going to have to modify my code a bit to get it working in Python 3, so it's not trivial to just test it on both versions to see which runs faster.  I'd need to be reasonably confident I will get a speed improvement before I spend the time updating my code to Python 3.
Try refining the algorithms or changing the data structures used. That's usually the best way to get an increase in performance.
Python 2.x vs 3.x Speed