gistfile1.py

>>> class AAA(object):
...     def go(self):
...         self.one = 'hello'
... 
>>> class BBB(object):
...     def go(self):
...         one = 'hello'
... 
>>> a1 = AAA()
>>> a1.go()
>>> a1.one
'hello'
>>> a2 = AAA()
>>> a2.one
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'AAA' object has no attribute 'one'
>>> a2.go()
>>> a2.one
'hello'
>>> b1 = BBB()
>>> b1.go()
>>> b1.one
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'BBB' object has no attribute 'one'
>>> BBB.one
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: type object 'BBB' has no attribute 'one'
>>> class BBB(object):
...     def go(self):
...         one = 'hello'
...         print one
...         self.another = one
... 
>>> b2 = BBB()
>>> b2.go()
hello
>>> b2.another
'hello'
>>> b2.one
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'BBB' object has no attribute 'one'