Why can't I increment my instance variable?

December 23, 2023

I want to increment the self.next after initialization. Such that, if var.next = 5 and I did var.incr, then var.next = 6

class node:
    def __init__(self, dataStored, nextNode):
        self.data = dataStored
        self.next = int(nextNode)
        self.display = (dataStored, nextNode)

    def incr(self):
        if self.next == -1:
            pass
        else:
            self.next += 1

x = node(0, 5)
x.incr()
print(x.display)

The output is (0, 5) // no change

I tried doing self.next = self.next + 1, but no difference.

It’s important that this program only uses built-in python functions as my exam board does not allow for imported functions

>Solution :

Since self.display is defined in the init method, you need to redefine it within the incr method to reflect any updates.

class node:
    def __init__(self, dataStored, nextNode):
        self.data = dataStored
        self.next = int(nextNode)
        self.dataStored = dataStored
        self.display = (dataStored, self.next)

    def incr(self):
        if self.next == -1:
            pass
        else:
            self.next += 1
            self.display = (self.dataStored, self.next)

x = node(0, 5)
x.incr()
print(x.display)