Newbie Q: Class Privacy (or lack of)

[Steve Jobless]

Hi,

I just started learning Python. I went through most of the tutorial at
python.org. But I noticed something weird. I'm not talking about the
__private hack.

Let's say the class is defined as:

  class MyClass:
    def __init__(self):
      pass
    def func(self):
      return 123

But from the outside of the class my interpreter let me do:

  x = MyClass()
  x.instance_var_not_defined_in_the_class = 456

or even:

  x.func = 789

After "x.func = 789", the function is totally shot.

Are these bugs or features? If they are features, don't they create
problems as the project gets larger?

TIA,

SJ