Using functions in classes?

[karlamadeus]

Hi guys, I am a bit new to OOP in general, and I was just wondering if I am going around what I want to do in the right way. I am making a small game to try to learn OOP and in this game I have several classes for different creatures, I create objects from these classes and add them to lists in a class called "Active". Now I am trying to create an actively updating list of all the creatures existing.

Would this be the right way of going about doing that:

class active:
    players = []
    goblins = []
    trolls  = []
    humans  = []
    bears   = []
    creaturelist = []

    def updatecreaturelist(self):
        for x in self.players:
            self.creaturelist.append(x)
        for x in self.goblins:
            self.creaturelist.append(x)
        for x in self.trolls:
            self.creaturelist.append(x)
        for x in self.humansr:
            self.creaturelist.append(x)
        for x in self.bears:
            self.creaturelist.append(x)

Also, what exactly is the difference between a class attribute and an instance attribute?
Any help much appreciated.
Thanks,
Karl

[griswolf]

Probably not the best thing to do, though it will apparently work.

Your second question indicates that you have a clue. Class attributes belong to the class itself, whereas instance attributes belong to an instance (of the class). So your lists are in the class: There is only one class "active". By accessing these lists through self, you are obscuring the facts. Legal, but in my opinion confusing.

I would prefer to put the empty lists into the class instance:

class Active(object):
    def __init__(self):
        super(Active,self).__init__()
        self.players = []
        self.goblins = []
        # etc
    def update_creature_list(self)
        self.creaturelist.extend(self.players)
        # etc

I think this is a better option. It allows you to have multiple "active" instances (perhaps to save for an "undo" option, or for some other reason) and it "just seems better to me".

[snippsat]

A little basic stuff about Class/OOP stuff that can be good to now.
Remeber it`s not called a function but a method,when it belong to Class.

class Active(object):
    ''' Special method __init__() is called auto when you makeing a object(acts as Constructor)'''
    def __init__(self):
        self.players = []
        self.goblins = []

    def put_first(self, first):
        '''This look like a function,put when belong to a Class is called a method'''
        return self.goblins.insert(0, first)

    def __str__(self):
        '''Special method __str__  get used when we use print on a object'''
        return 'players: %s goblins: %s' % (self.players, self.goblins)

#Now let test out this Class in IDLE

Here we se two empty list because stuff under __init__ get called auto when we make an object

>>> a_object = Active() #Class instance,we are making a object
>>> print a_object #print find __str__,and print out object info
players: [] goblins: []
>>>

We put in a couple of goblins.

>>> a_object.goblins.append('Grunt')
>>> a_object.goblins.append('Killer')
>>> print a_object
players: [] goblins: ['Grunt', 'Killer']

Last we are using method put_first to place a goblin first in the list.

>>> a_object.put_first('Gotar')
>>> print a_object
players: [] goblins: ['Gotar', 'Grunt', 'Killer']
>>>