How to define a class in Python 2?

Question

I'm just starting to learn classes and objects in Python and I've looked online to find an answer to why it is coming up with the error: "nameError, 'Bedroom' is not defined" and theres been many answers and explanations in that I have to define the class but I just can't see what I'm personally doing wrong its driving me nuts and I know its probably a really stupid mistake, but you learn from them I suppose.

prompt = "> "

class Start():
    print "Project Storm v0.01"
    print "Press Enter to Play"
    raw_input(prompt)
    bedroom = Bedroom(Room)

class Room():
    def enter(self):
        pass

class Bedroom(Room):
    def enter(self):
        print "You wake up dazed and confused with no memory of how you got here."
        print "You find yourself in a dark bedroom with a closed door and a small lamp on the side."

Move your classes into the order Room, Bedroom, Start. The order of definitions matter http://stackoverflow.com/questions/4937532/python-name-resolution-order-of-function-defs — Cory Kramer, Oct 24 '14 at 19:27
The compiler says it all. You try to use `Bedroom` when it's undefined yet. The interpreter doesn't read ahead. — luk32, Oct 24 '14 at 19:27
#inspectorG4dged #Cyber thank you worked a charm but just wondering why that actually works and what difference that makes to how the code is run. — KingSwan, Oct 24 '14 at 19:28
That is common in many languages, it is (one of) the main reasons that C and C++ use header files. The compiler works top-down, how is it supposed to know that some new class `Bedroom` is coming up if it hasn't reached that point yet? — Cory Kramer, Oct 24 '14 at 19:29
maybe learning the basics would be a good step before using classes https://docs.python.org/2/tutorial/classes.html — Padraic Cunningham, Oct 24 '14 at 19:32

Adam Smith · Accepted Answer · 2014-10-24T19:36:32.413

Try this instead:

class Room():
    def enter(self):
        pass

class Bedroom(Room):
    def enter(self):
        print "You wake up dazed and confused with no memory of how you got here."
        print "You find yourself in a dark bedroom with a closed door and a small lamp on the side."

class Start(): # shouldn't this be Game() or something?
    print "Project Storm v0.01"
    print "Press Enter to Play"
    raw_input(prompt)
    bedroom = Bedroom(Room)
    # Bedroom has now been defined, so it knows what that is.

However it's kind of a strange structure. Give me a minute I can come up with something a lot more extendable....

PROMPT = "> "

class Room():
    def __init__(self, msg):
        self.msg = msg
    def enter(self):
        print msg

class Bedroom(Room):
    pass
    # there's not actually anything special about this now, since all Room objects
    # will have a message. Maybe you have something special here?

class Game():
    def __init__(self):
        print "Project Storm v0.01"
        print "Press Enter to Play"
        raw_input(PROMPT) # all caps for constants
        self.rooms = {}
        self.rooms["bedroom"] = Bedroom("""You wake up dazed and confused with no memory of how you got here.
You find yourself in a dark bedroom with a closed door and a small lamp on the side.""")
    def start(self):
        self.rooms['bedroom'].enter()

if __name__ == "__main__":
    game = Game()
    game.start()

Now you can more easily add on rooms with their own descriptions and pace your game appropriately.

yes Padraic ive sorted that out since but its more the fact i had to change the order was confusing me. thanks for all the help! — KingSwan, Oct 24 '14 at 19:37
@KingSwan if you'd put your initialization logic in `__init__` (e.g. inside `Game.__init__` goes: `self.bedroom = Bedroom()`), it wouldn't matter what order it was in! :) — Adam Smith, Oct 24 '14 at 19:38
oh i see yes that makes sense also thanks for the great answer very helpful and yes the bedroom(Room) will have something special in it eventually :P — KingSwan, Oct 24 '14 at 19:42
@KingSwan basically it would work that way because the compiler doesn't introspect a function until it's called, and by then `Bedroom` would be defined REGARDLESS OF ORDER. — Adam Smith, Oct 24 '14 at 19:43

How to define a class in Python 2?

1 Answers1