Stepping Through inner_returned()

00:00 In the previous lesson, you stepped through most of this code that we have here on the page, but you stopped shortly before calling inner_returned().

00:07 So now this is going to be the final call to the inner() function object that you returned from the outer() function call. And what happens is, again you will open up a new local scope, just like you did during the other two calls to inner().

00:23 And now you still have access to the message variable, as you can see here through the nonlocal scope of the inner() function.

00:30 And this might be surprising that this is going print world a second time, because you might wonder, “Okay, so the call to the outer() function is over, so that scope is closed.” You don’t see the window here anywhere anymore, right?

00:41 Like this scope is gone. But because inner() was defined inside of the outer() function, it also has access to the variables that were defined inside of the outer() function, through the so-called nonlocal scope.

00:54 And because the last value that message got inside of this function definition was 'world', it still points to that same string.

01:02 So now if you continue execution, you’ll see Python evaluates the print() call, evaluates message to 'world', and then it’s ready to print it out, and it shows up on your console. Again, the print() function returns None and also, inner_returned(), because it’s still that function object up here that you’re working with, also returns None.

01:24 And that finishes the execution of your script. So now your output is one time hello from the first call to the inner() function,

01:33 one time world from the second call to the inner() function, which both still happen inside of the outer() function.

01:40 And then the third time, the third call to the inner() function, which I called here inner_returned() because it’s the returned function object, prints out again the string world because this was the last value that message got inside of the definition of the outer() function and inside of the body of the outer() function.

02:00 And the inner() function keeps a knowledge of what that variable is through the nonlocal scope of that function. This was a lot to step through, and I hope it made it a little easier by just giving those functions and variables easier-to-understand names and also by using Thonny and seeing the different scopes pop up as separate windows.

02:21 That’s about it for this code snippet, but in the next lesson, we’re going to dig a little deeper and figure out where does this variable get stored in Python, like how come does this inner() function object still has access to this nonlocal variable and where does it live?

02:38 And you’ll jump a little into an interpreter session and play around with it to figure out how Python handles this internally.