Python: How can I fix this attribute error?

Question

class zzz:
def __init__(self,n):
self.x = n
def set_y(self):
self.y=self.x * 2
obj = zzz(2)
print(obj.x + obj.y)

Answer 1

you can add self.set_y() to the __init__ method:

def __init__(self,n):
self.x = n
self.set_y()

Answer 2

self.y doesn't exist until you call obj.set_y().

obj = zzz(2)
obj.set_y()
print(obj.x + obj.y)

Answer 3

Russ is right. Also, it's better to initialize that value in the __init__ method, some editors (like pycharm) will give you a warning for that