That's not true, an initial underscore is simply used as the convention to indicate that something is private:
>>> class Foo(object):
... def __init__(self):
... self._bar = 48
...
>>> a=Foo()
>>> a._bar
48 >>> class Foo(object):
... def __init__(self):
... self.__a = 42
... def look_here(self):
... print self.__a
...
>>> f = Foo()
>>> f.__a
Traceback (most recent call last):
File "<stdin>", line 1, in ?
AttributeError: 'Foo' object has no attribute '__a'
>>> f.look_here()
42 >>> class Foo(object):
... def __do_something(self):
... print 'something was done'
...
>>> f = Foo()
>>> f.__do_something()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'Foo' object has no attribute '__do_something'
>>> f._Foo__do_something()
something was doneThis is a good example of Python making it harder for you to do the wrong thing. Sure.. you could access that "private" attribute, but you have to do it in a way that isn't obvious, and definitely more hard to read.