difference between variables inside and outside of __init__()

Question

Is there any difference at all between these classes besides the name?

class WithClass ():     def __init__(self):         self.value = "Bob"     def my_func(self):         print(self.value)  class WithoutClass ():     value = "Bob"      def my_func(self):         print(self.value) 

Does it make any difference if I use or don't use the __init__ method for declaring the variable value?

My main worry is that I'll be using it one way, when that'll cause me further problems down the road.

Answer 1

Variable set outside __init__ belong to the class. They're shared by all instances.

Variables created inside __init__ (and all other method functions) and prefaced with self. belong to the object instance.

Answer 2

Without Self

Create some objects:

class foo(object):     x = 'original class'  c1, c2 = foo(), foo() 

I can change the c1 instance, and it will not affect the c2 instance:

c1.x = 'changed instance' c2.x >>> 'original class' 

But if I change the foo class, all instances of that class will be changed as well:

foo.x = 'changed class' c2.x >>> 'changed class' 

Please note how Python scoping works here:

c1.x >>> 'changed instance' 

With Self

Changing the class does not affect the instances:

class foo(object):     def __init__(self):         self.x = 'original self'  c1 = foo() foo.x = 'changed class' c1.x >>> 'original self'