replace operates on a specific string, so you need to call it like this
removeSpecialChars = z.replace("!@#$%^&*()[]{};:,./<>?\|`~-=_+", " ")
but this is probably not what you need, since this will look for a single string containing all that characters in the same order. you can do it with a regexp, as Danny Michaud pointed out.
as a side note, you might want to look for BeautifulSoup, which is a library for parsing messy HTML formatted text like what you usually get from scaping websites.