thanks for this good explanation. I spent a few hours trying to find my bug and I finally used a debugger… then it was easy to see that the value was not the expected one. I wish I had used the debugger earlier!

The “closure factory” solution is quite straightforward. But I wouldn’t have thought of the keyword arguments workaround, which is concise but a bit cryptic. The kind of thing I’d leave a comment for in my code.

It’s kind of funny how one common gotcha (how default values are being evaluated) can be used as a workaround for another gotcha.