>>> bar
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'bar' is not defined
>>> class Foo:
...     global bar
...     bar = 42
... 
>>> bar
42
>>> Foo.bar
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: type object 'Foo' has no attribute 'bar'