Why should input(prompt="hello:") fail?

[zhi]

Really confused, when I use keyword style argument as following:

>>> input(prompt="hello")

Traceback (most recent call last):
  File "<pyshell#52>", line 1, in -toplevel-
    input(prompt="hello")
TypeError: input() takes no keyword arguments

While the library reference says the function is: input( [prompt]) 
so, it should work.:(

I am using python 2.3 for windows.
Have anyone tried this? 
I am new to python, please help me, thanks.