I won't bite on the feature/bug argument, but it's enough of a foot-gun that I have tracked down no less than 3 real world bugs relating to it in large python c

I won't bite on the feature/bug argument, but it's enough of a foot-gun that I have tracked down no less than 3 real world bugs relating to it in large python code bases. Usually when people use an empty list literal as default and shit gets real when it retains values on the next call. When performing Python interviews I usually try to have that behavior come up in the coding question - not to quiz for trivia so much as to get a feeling for adding on battle-scar bonus points. In practice, for any non plain-ol-data defaults I just have it default to None and handle it in logic. Totally understand why it may be useful for introducing a persistent store to a function, but as a matter of taste I like to do that in an explicit decorator if needed.