Variable naming in Python classes

Question

So I started using python very recently. I am doing a small project involving classes. I for the most part have the conventions down like using self... etc. What I haven't figured out quite yet is the name mangling which may be related to my question.

Here is some code that forms a class to create a turn object that i can intilize in the beginning of a battle and allows me to switch turns periodically. (the game is going to be a pokemon battle simulator)

class turn:

    TURNS = ("player","computer")
    curr=0

    def __init__(self): 
        self.currentTurn=turn.TURNS[turn.curr]

    def getTurn(self):
        return turn.TURNS[turn.curr]

    def switch(self):
        if turn.curr == 0: 
            turn.curr = 1 
        else:   
            turn.curr = 0

        if turn.curr==0: 
            print "It's your move! \n"

        self.currentTurn=TURNS[turn.curr]

So my question is this:

Is there any feature of python that would allow me to omit the class name when referring to the class vairables. I feel like it should know to look within the class definition for those variables but it doesn't. Also, If I want to use a helper method within the same class, i seem to have to prefix that with self.

Is there anyway around this?

Martjin, I was in the midst of editing when you fixed the errors for me, thank you. The SO editor put those stars in for me when I tried to make all the instances of "turn." bold — Luke
– Luke, Commented Jul 22, 2014 at 12:52
"Explicit is better than implicit." Live with Python's dogmas like this one. What might appear as a nice feature to you might be a lot of trouble for the next developer trying to understand your code. — Alfe
– Alfe, Commented Jul 22, 2014 at 12:53
@user3756732: There is no support for formatting in a code block; outside a codeblock ** makes things bold. — Martijn Pieters
– Martijn Pieters, Commented Jul 22, 2014 at 12:54

Martijn Pieters · Accepted Answer · 2014-07-22 13:07:36Z

1

You can reference the current class with type(self) or self.__class__. Take into account that that value changes as a class is subclassed.

So:

class turn(object):
    def __init__(self): 
        cls = type(self)
        self.currentTurn = cls.TURNS[cls.curr]

    def getTurn(self):
        cls = type(self)
        return cls.TURNS[cls.curr]

    def switch(self):
        cls = type(self)
        cls.curr = 1 - cls.curr

        if cls.curr == 0: 
            print "It's your move! \n"

        self.currentTurn = cls.TURNS[cls.curr]

but if you were to subclass turns, then setting cls.curr will be done on the subclass, not the turn parent class when you call subclass().switch().

You can also use the self.__class__ attribute, but using a built-in function lets you keep the code more readable.

However, note that as long as there are no instance attributes with the same names, you can refer to your class attributes on self as well; the following works too:

class turn(object):
    def __init__(self): 
        self.currentTurn = self.TURNS[self.curr]

    def getTurn(self):
        return self.TURNS[self.curr]

    def switch(self):
        cls = type(self)
        cls.curr = 1 - cls.curr

        if self.curr == 0: 
            print "It's your move! \n"

        self.currentTurn = self.TURNS[self.curr]

Setting class attributes still requires that you do so directly on the class, not self, however.

edited Jul 22, 2014 at 13:07

answered Jul 22, 2014 at 12:51

Martijn Pieters

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5 Comments

Luke Over a year ago

By "subclassing" you mean if I were to put another class definition within that class?

Martijn Pieters Over a year ago

@user3756732: you can create a derived class, that reuses everything in turn, adding on to it, or replacing functionality. class subclass(turn): pass is a useless subclass that just inherited everything without adding.

Martijn Pieters Over a year ago

@user3756732: see Inheritance in the Python toturial.

Martijn Pieters Over a year ago

@user3756732: Btw, I am making the assumption that you are using Python 3 here; in Python 2, make sure you inherit from object (new-style classes), otherwise type(self) won't work.

Luke Over a year ago

Thanks this was helpful, and I know about inheritance, that idea just didn't register in my head at the moment, it seemed to obvious lol. Thanks for editing to make more clear

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