Not to mention that a lot of these performance improvements, while sane, are on the order of milliseconds of improvement. Unless you're doing one of these unoptimized approaches thousands or millions of times in a tight loop you're probably not saving a substantial amount of time/energy/computation. Premature optimization is still the root of all evil!
If you want an actual performance improvement in Python code that most people wouldn't necessarily expect: consider using regexes for even basic string parsing if you're doing a lot of it, rather than doing it yourself (e.g. splitting strings, then splitting those strings, etc.); while regexes "feel" like they should be more complicated and therefore slower or less efficient, the regex engine in Python is implemented in C and there's a decent chance that, with a little tweaking, even simple string processing can be done faster with a regex. Again only important in a hot loop, but still.
If you want an actual performance improvement in Python code that most people wouldn't necessarily expect: consider using regexes for even basic string parsing if you're doing a lot of it, rather than doing it yourself (e.g. splitting strings, then splitting those strings, etc.); while regexes "feel" like they should be more complicated and therefore slower or less efficient, the regex engine in Python is implemented in C and there's a decent chance that, with a little tweaking, even simple string processing can be done faster with a regex. Again only important in a hot loop, but still.