What ought to persist after a program is run?

[Thomas Philips]

Here's a very simple program with an odd twist:
class Player(object):
    def __init__(self,name):
        self.name = name

hero = Player("A")
print "hero",hero

If I run it in IDLE and then type dir() at the prompt, I get
>>>['Player', '__builtins__', '__doc__', '__name__', 'hero']

However, if I modify the program as follows
class Player(object):
    def __init__(self,name):
        self.name = name
def main():
    hero = Player("A")
    print "hero=",hero
main()

and then run it in IDLE and type dir at the prompt, I get
>>>['Player', '__builtins__', '__doc__', '__name__']

Why does 'hero' not appear in the workspace directory when main() is
invoked and vice versa?

Thomas Philips