[Tutor] Methods that return instances of their own class?

[David Perlman]

Oh my goodness, it really is that easy!  I guess I assumed that was  
too simple to work.  Silly me.  Thanks Andre!

On Oct 15, 2009, at 10:31 AM, Andre Engels wrote:

> On Thu, Oct 15, 2009 at 5:14 PM, David Perlman <dperlman at wisc.edu>  
> wrote:
>> I'm trying to figure out how to define a class so that its  
>> instances have a
>> method that return a different object of the same class.
>>
>> In particular, I'm trying to run a simple prisoner's dilemma game,  
>> and I
>> want to make a "game" object that has a method which returns the  
>> "game"
>> object with the payoffs reversed; that is, the payoff matrix from  
>> the other
>> player's point of view.  Basically a kind of transpose which is  
>> specific to
>> this application.
>>
>> class Payoffs(list):
>>    def __init__(self, value=None):
>>        list.__init__(self)
>>        if value==None: # use a default prisoner's dilemma
>>            value=[[(3,3),(0,5)],
>>                   [(5,0),(1,1)]]
>>        self.extend(value)
>>
>>    def __repr__(self):
>>        l1="Your Choice:   Cooperate    Defect\n"
>>        l2="My choice:   -------------------------\n"
>>        l3="Cooperate    | (% 3d,% 3d) | (% 3d,% 3d) |\n" % (self[0] 
>> [0][0],
>> self[0][0][1], self[0][1][0], self[0][1][1])
>>        l4="              ----------------------- \n"
>>        l5="Defect       | (% 3d,% 3d) | (% 3d,% 3d) |\n" % (self[1] 
>> [0][0],
>> self[1][0][1], self[1][1][0], self[1][1][1])
>>        l6="             -------------------------\n"
>>        return l1+l2+l3+l4+l5+l6
>>
>>    def transpose(self):
>>
>> And that's where I'm at.  How can I have the transpose method  
>> return another
>> Payoffs object?  Here's the beginning of it:
>>
>>    def transpose(self):
>>        trans=[[(self[0][0][1],self[0][0][0]),
>> (self[1][0][1],self[1][0][0])],
>>               [(self[0][1][1],self[0][1][0]),
>> (self[1][1][1],self[1][1][0])]]
>>
>> But now "trans" is type list, not type Payoffs.  I don't know how  
>> to get it
>> into a Payoffs object so that the transpose will have my other new  
>> methods.
>>
>>
>> Thanks very much.  I searched for answers but I'm not sure what  
>> this would
>> be called, which made it hard to find.
>
> I may be thinking too simple, but isn't this just:
>
> def transpose(self):
>     trans=[[(self[0][0][1],self[0][0][0]), (self[1][0][1],self[1][0] 
> [0])],
>               [(self[0][1][1],self[0][1][0]), (self[1][1][1],self[1] 
> [1][0])]]
>     return Payoffs(trans)
>
>
> -- 
> André Engels, andreengels at gmail.com

--
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