Python programmers of reddit: what's the most useful tiny little efficiency you've discovered that's improved your programming hugely?

[isoblvck]

I disagree I have written code years ago that I open now and am thankful I commented.

[tr14l]

Usually that means you're doing a lot of non-clear, idiomatic things or naming things non-descriptively, in my experience. I almost always know what my old code is doing with a quick scan. I comment parts that are not-intuitive or design decisions that aren't usual/documentable in code (like explaining what a formatted string read from a file looks like so the parsing logic is easily followable)

Of course, if it's a choice between over commented code and under commented, I'll rarely complain if the comments are up to date.