correct way to define class variables in Python [duplicate]

I noticed that in Python, people initialize their class attributes in two different ways.

The first way is like this:

class MyClass:
  __element1 = 123
  __element2 = "this is Africa"

  def __init__(self):
    #pass or something else

The other style looks like:

class MyClass:
  def __init__(self):
    self.__element1 = 123
    self.__element2 = "this is Africa"

Which is the correct way to initialize class attributes?