Question

I’m currently learning python using Learn Python the Hard Way and really enjoying it. In one of the lesson examples, there is a use of ‘return’ that I fail to grasp.

The lesson I’m stuck on is Exercise 43: Gothons From Planet Percal #25. I understand that when the game is first run next_room_name is set to central_corridor and so central_corridor() is called during the first loop under play().
What I don’t understand is how self.start get’s re-assigned.

For example, in the instance of death being returned under central_corridor(). After the return on line 49, we’re back in the play(self): while True loop. The first line is next_room_name = self.start As far as I know, self.start still equals central_corridor, but it apparently is now equalling death.

Does this mean that after death is returned, and still in the while loop under play(), the object Game() has been reinitialized, the __init__ being fed the results of the return? I’m confused how the next_room_name = self.start under __init__ is being reassigned to death when we’re technically still in the play(self): while True loop and haven’t exited it. I guess I’m confused as to where death is being returned to.

Answer 1

So let’s walk through a few steps of it up until the while loop:

a_game = Game("central_corridor")
a_game.play()

Here we instantiate a_game, with the start_value = central_corridor. So far, so good 🙂 Now we run a_game.play():

def play(self):
    next_room_name = self.start

    while True:
        print "\n--------"
        room = getattr(self, next_room_name)
        next_room_name = room()

As you correctely stated, next_room_name gets assigned the value central_corridor, and then the while loop begins.

This may be the important part to get – the while loop only executes the while piece and everything indented undnerneath it – next_room_name is not reassigned to self.start each time. Instead, we define room as the attribute next_room_name (which is central_corridor), and then run the method of the same name. The return value of that method (let’s say death) is then used in the next loop, meaning that room = death, next_room_name= the result of death(), which prints a random quip and then exits. If the name were another room, it would continue the loop.