Why can't I restore my redirected stdout?

[Raymond Ng Tong Leng]

I am trying to implement a verbose and quiet mode in my Python script. So I
wrote the following class:

class Quiet:
    def write(self, data):
        pass

Then I set sys.stdout to Quiet by:

>>> sys.stdout = Quiet()
>>> print 'hello'
>>>

'hello' doesn't come out which is what I want. But, when I tried to restore
sys.stdout's original settings:

>>> sys.stdout = sys.__stdout__
>>> print 'hello'
>>>

'hello' is not printed either! How do you restore sys.stdout to its original
settings? Also, I was wondering, are there other ways to suppress
sys.stdout? I'm just curious whether I could suppress sys.stdout without
redirecting to a class. It seems to me that I should be able to redirect
sys.stdout to a null device or something. Thanks!