problem while going through a tutorial

[Simon Schuster]

I'm new to python, and almost new to programming in general. I'm at
http://www.pasteur.fr/formation/infobio/python/ch04.html in that
tutorial, and my 'count' function (if it's called a function?) isn't
working suddenly.

>>> x = "fljshfjh"
>>> x
'fljshfjh'
>>> count(x, 'h')
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
NameError: name 'count' is not defined

I'm not sure what changed, because it used to work. anyhow thanks a lot!

chris