python objectlist adds to all objects

Question

I'm trying to have a class (dprObject) that is a container for several dprVariables each variable has a list with integers (for now) but when I change something to one variable, it changes to all the other variables

in this case, the output I get is

score: 5, 6, 3, 4, position: 5, 6, 3, 4,

but I want to see

score: 5, 6, position: 3, 4,

#!/usr/bin/python3

import pprint

def main(): 
    d = dprObject() #new dpr object
    score = dprVariable(d, "score") #new dpr variable
    score.set(5) #set value
    score.set(6)

    position = dprVariable(d, "position")
    position.set(3)
    position.set(4)

    print(d)
    print("done")

class dprObject:
    var = [] 
    t = 0
    def __init__(self):
        pass

    def __str__(self):
        toReturn = ""
        for v in self.var:
            toReturn += v.toString()
        return toReturn

    def tick(self):
        self.t += 1

    def addVariable(self,v):
        self.var.append(v)


class dprVariable:
    name = ""
    value = None
    val = []

    def __init__(self,d,name):
        self.name = name
        d.addVariable(self)

    def __str__(self):
        return self.toString()

    def toString(self):
        toReturn = self.name + ": "
        for v in self.val:
            toReturn += str(v) + ", "
        return toReturn

    def set (self, value):
        self.value = value
        self.val.append(value)

#class DprValue:



if __name__ == "__main__":
    main()

any help would be appreciated thanks

RichieHindle · Accepted Answer · 2013-06-16 20:38:09Z

1

This code:

class dprVariable:
    ...
    val = []

makes val a class variable, shared between all instances of dprVariable. To have one val per instance, you need to do this:

class dprVariable:
    def __init__(self, ...):
        self.val = []

(dprObject has the same problem.)

answered Jun 16, 2013 at 20:38

RichieHindle

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