Question

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Assign a value to class variable is assiging it for all instances of that object

I need a help. I am used to java development and new I am starting python. And I write a simple class which contain a list of string. and In the main function I create a list of this object and I would like to print the content of the list of object. But my function print all the string of all the object together.
Here is an example

class FastData:
        name=''
        lines=[]

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

        def setName(self,name):
                self.name = name

        def addLine(self, line):
                self.lines.append(line)

        def getLines(self):
                return self.lines

        def getName(self):
                return self.name

        def printList(self):

                for myline in self.lines:
                        print myline

if __name__ == '__main__':
    listes = []

    newData = FastData("Single")
    newData.addLine("1")
    newData.addLine("2")

    listes.append(newData)



    newData1 = FastData("Double")
    newData1.addLine("111")
    newData1.addLine("222")
    listes.append(newData1)

    for myList in listes:
        print myList.getName()
        myList.printList()

and Here is what I got like output

Single
1
2
111
222

Double
1
2
111
222

Thank for your help

Thathug

Answer 1

In your code, all instances of FastData share the same lines object. Fix it like so:

class FastData:

    # note that I've removed `name' and `lines' from here

    def __init__ (self, name):
            self.name = name
            self.lines = []

The reason your code worked the way it did was that lines was a property of the class, not of each individual instance of the class.