@loke I like optimizing stuff when programming, sometimes a bit too much, but have to agree with this. When you really need performance, change programming language.
One problem I see a lot with Python is that the language purists have gone a bit too far, developers pushed by linters (e.g. 'pylint') to use comprehensions and other elegant solutions which in some cases creates unnecessary (or undetected) loops within loops (effectively making the code O(N**2)) because using many variables is somehow a bad coding style. I agree source code should be readable, but there has to be a balance with performance.