It doesn't make a copy. It creates a special object (which you don't see unless you're digging in the internals) called a "cell" which holds a reference to the

It doesn't make a copy. It creates a special object (which you don't see unless you're digging in the internals) called a "cell" which holds a reference to the object for as long as the function exists. To see for yourself, look at `somefunc.func_closure` -- it'll be `None` on regular functions, and a tuple of cells on a closure function.