Why is score instance variable not decreasing when it should in python

Every time you call Player() you're creating a new player. So when you do

Player().score = Player().score - 10 print(Player().score) 

it's roughly equivalent to:

temp_player1 = Player() temp_player2 = Player() temp_player1.score = temp_player2.score - 10 temp_player3 = Player() print(temp_player3.score) 

As you can see from that, there are 3 different players, so you're never decrementing any player's score, and then you're printing a different player's score.

You need to add a player attribute to the Circle, then it can use self.player instead of creating a new player each time.

import turtle as t import random class Circle: def __init__(self,size): self.size = size #self.speed = speed self.circle = t.Turtle() self.ypos = 300 this.player = Player() def size_color(self): self.circle.color('red') self.circle.shape('circle') self.circle.shapesize(self.size,self.size,1) #positions circle random x top y def posit(self): number = random.randint(-340,340) self.circle.ht() self.circle.penup() self.size_color() self.circle.goto(number,self.ypos) self.circle.st() #substracts from y position for falling effect #should substract from score as well def drop(self): self.posit() while True: self.ypos = self.ypos- 4 self.circle.sety(self.ypos) if self.ypos <= -300: self.player.score = self.player.score - 10 print(self.player.score) self.ypos = 300 self.posit() class Player: def __init__(self,score=200): self.score = score def display_screen(): window = t.Screen() window.bgcolor('black') display_screen() c = Circle(2) c.drop() 

Barmar stole my answer. Use what he said, however don't forget to change this.player to self.player as he made a tiny mistake, probably because of other programming languages.