Checking performance of programs

Question

What is a good way of checking the performance (running time, running space, etc) of programs?
Whenever I use the timeit module for timing and comparing the runtime of two codes, there always seems to be a trend where the first code that is timed is slower than the rest or something like that. I’m not sure if I’m using it correctly. Here is an example.
https://code.sololearn.com/czdIuUwupePb/?ref=app

Answer 1

When I ran your code a few times, I got very mixed results, the first test 'won' plenty.