Python: Scrape Data from Web after Inputing Info

Could anyone help me revise this Python program to correctly submit information to the "Date Range" query, and then extract the "Close" return data. I am scraping data from the following url:

http://finance.yahoo.com/q/hp?s=%5EGSPC+Historical+Prices

And this is my current code, which returns "[ ]".

 from lxml import html
import requests


def historic_quotes(symbol, stMonth, stDate, stYear, enMonth, enDate, enYear):
    url = 'https://finance.yahoo.com/q/hp?s=%s+Historical+Prices' % (symbol)

    form_data = {
        'a': stMonth,  #00 is January, 01 is Feb., etc.
        'b': stDate,
        'c': stYear,
        'd': enMonth,  #00 is January, 01 is Feb., etc.
        'e': enDate,
        'f': enYear,
        'submit': 'submit',
    }
response = requests.post(url, data=form_data)

tree = html.document_fromstring(response.content)
p = tree.xpath('//*[@id="yfncsumtab"]/tbody/tr[2]/td[1]/table[4]/tbody/tr/td/table/tbody/tr[2]/td[7]/text()')
print p

historic_quotes('baba',00,11,2010,00,11,2012)

I am an overall Python novice, and greatly appreciate any and all help. Thanks for reading!