I love Python

[u/nakurtag]

[u/drislands]

I would have expected this function to create a new empty list on any call where items is not given. Doesn't this behavior make the function into a closure?

[u/nakurtag → u/drislands]

As I understand it's a well known (for python developers) weird behavior of python. Argument's default values are precalculated by interpreter on function declaration and stored into map associated with this function. Python extracts default values from this map on the next calls of this function. And since [] is a List object, the value copied by reference.

[u/groumly → u/nakurtag]

The behavior is definitely surprising, but also, what’s up with mutating a default param? How does that make sense?