It may be an easy mistake to make but using None is more consistent and efficient to detect. You can use "if x is None:" for any type; whereas, a function may

It may be an easy mistake to make but using None is more consistent and efficient to detect. You can use "if x is None:" for any type; whereas, a function may or may not want to allow empty strings (or even empty lists) and it is easy to use a None check to decide when to apply the desired default.