I’ve never thought that leaking this type of implementation detail into the return value (and return type!) was a nice solution. I like the double closure better, and one can shorten it a bit with a lambda.

For those who prefer a functional style, functools.partial can also solve this problem.

(I use Python, and I like a lot of things about Python, but I don’t like its scoping rules at all, nor do I like the way that Python’s closures work. I would use a double lambda.)