What does "Return" do in Python?

Question

What "really" the return does in Python, mainly in recursive functions. Ex. factorial:

def fatorial(n):
    if n==1:
        return n
    return fatorial(n-1) * n

Answer 1

As in any language mainstream, the return ends the execution of the current function, returning exactly to the point where it was called.

Eventually it can return a value as a result of the function, ie where the function was called will have the return value used in the expression built there.

There’s nothing special about return when it is used in recursive functions, the functioning is exactly the same. In a recursive function the calls accumulate and the returns occur later always returning to the same point, but in different states. Obviously at some point you need to stop making recursive calls, otherwise you have an infinite recursion and pop the stack.

As it is not a special case, if there is a large number of calls, and each call keeps its own state (values of local variables), it fills the pile of the application and may give such stack overflow.

Some languages/compilers do optimizations to avoid this overflow in cases of too much recursion, which also helps in efficiency.

Answer 2

It returns the value of the function. In the specific case of recursive functions, it, besides returning the value (which can also be a null value None), will also return the control flow to the caller function.