Ah yes, the ol' default empty list Python gotcha, it bit me I think about 10 years ago, and ever since, sadly I've written code like this so many times it's not

Ah yes, the ol' default empty list Python gotcha, it bit me I think about 10 years ago, and ever since, sadly I've written code like this so many times it's not funny: def fun(a = None): _a = a if a is not None else []