> How do you automatically go from sort( ... some elaborate compare function ...) to sort(key=some completely different function). Yes, there's a wrapper Yes,

> How do you automatically go from sort( ... some elaborate compare function ...) to sort(key=some completely different function). Yes, there's a wrapper Yes, there's a wrapper. You use it, add a comment "this is wrapped in the migration to 3" and move on. > How do you automatically infer the intention of somedict.keys()? Is it going to be used as a list or as an iterator? If it's being iterated on first thing, it's an iterator. If list methods are called on to it, it's a list. This just hasn't been a problem for us, sure, it took some looking at, but it wasn't more than 30 seconds per case. > I have the feeling that your positive experience with 2to3 might rather be the exception than the rule for old and big code bases. Maybe so, but the codebase was ten years old and hundreds of thousands of lines.