How do I make a defaultdict safe for unexpecting clients?

Question

Several times (even several in a row) I\'ve been bitten by the defaultdict bug: forgetting that something is actually a defaultdict and treating it like a regular dictionary

Answer 1

You can prevent creation of default values by assigning d.default_factory = None. However, I don't quite like the idea of object suddenly changing behavior. I'd prefer copying values to the new dict unless it imposes severe performance penalty.