Alex Hall wrote:
On 5/22/10, MRAB <pyt...@mrabarnett.plus.com> wrote:
Lanny wrote:
The answer may be right infront of me but I really can't figure this
out.
I'm trying to build a interactive fiction kind of game, silly I know
but I
am a fan of the genre. I'm trying to build up an index of all the
rooms in
the game from an outside file called roomlist.txt. The only problem is
that
every room ends up having four exits. Here's the code.
class room() :
room_id = 'room_id'
name = 'room'
description = 'description'
item_list =
exits = {}
> visits = 0
These attributes are being defined as belonging to the class, so they
will be shared by all the instances of the class. This isn't a problem
for immutable items such as strings, but is for mutable items such as
dicts. In short, all the rooms share the same 'exits' dict.
You should really define the instance attributes (variables) in the
'__init__' method.
I just ran into something similar to this in my Battleship game. I had
a Craft class, which defined attributes for any craft (a recon plane,
a submarine, a battleship, and so on). One such attribute was a
weapons list, much like your exits dictionary; I would assign a couple
weapons to a battleship, but suddenly all my ships and airplanes had
those same weapons. What the great people on this list said to do was
something like this:
class Room():
def __init__(self, exits):
if exits==None:
self.exits={}
else:
self.exits=exits
In this way, you can create a new Room object with exits,
r=Room(exits_dict)
or you can create a Room with no exits, and add them later:
r2=Room()
r2.exits["exit1"]="doorway"
but the code in the __init__ method, which will get called as soon as
you create a new Room object, ensures that passing an exits dictionary
will set that instance's exits to what was passed in, while passing
nothing will create a room with an empty dictionary (the if
statement). I hope this made some sense!
[snip]
It does when when you want 'exits' to take a default value which is a
mutable type (and you don't want it shared by all instances).
class Room:
def __init__(self, exits=None):
if exits is None:
self.exits = {}
else:
self.exits = exits
Otherwise, you're fine without the if ... else.
Duncan
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