Question

Is there a difference between

class Foo(object):
    bar = 1
    def __init__(self):
        ... etc.

and

class Foo(object):
    def __init__(self):
       ... etc.

Foo.bar = 1

In both cases bar is a property of the class and it is same for all instances of the class, right?

Answer 1

I’d say that the only difference is that in the second case, Foo.bar doesn’t exist until the Foo.bar = 1 statement is executed while in the first case is already available when the class object is created.

That’s probably a small difference without any effect in your code (unless there is some code that requires Foo.bar before it’s available in the second case). However, I’d say that the first option is better in terms of readability since you don’t have to scroll down to know the attributes for your class, they’re already there.