#Now that we know the format of the web pages
#returned by Yahoo! finance,
#we can write an application that extracts the
#stock price information and displays it in
#a useful way.  This function takes the stock
#ticker code as a parameter, returns 0 if
#a nonexistent ticker code is passed, -1 if
#the information is not in the expected format
#(for example, if the layout of the website
#has changed), and otherwise a list of two
#strings, giving the time and the stock price.
from urllib import *
def getStockPrice2(stock_code):
  webstream=urlopen("http://finance.yahoo.com/q?s="+stock_code)
  results=webstream.readlines()
  webstream.close()
#if there's an invalid stock identifier,
#then line 92 of the page contains error information
  if len(results)>92 and results[92].find("There are no") != -1:
    result = 0
#otherwise, line 9 contains the price and time of day,
#which we now proceed to extract from the  string
  else:
    priceline=results[9]
    loc1=priceline.find("yfs_t10")
    loc2=priceline.find(">",loc1)
    loc3=priceline.find("<",loc2)
    loc4=priceline.find("yfs_l10")
    loc5=priceline.find(">",loc4)
    loc6=priceline.find("<",loc5)
    if -1 in [loc1,loc2,loc3,loc4,loc5,loc6]:
#if this happens, then the website's format must
#have changed
      result=-1
    else:
      time=priceline[loc2+1:loc3]
      price=priceline[loc5+1:loc6]
      result=[time,price]
  return result

def testGetStockPrice2(stockCode):
  v=getStockPrice2(stockCode)
  if v==0:
    print "Invalid stock code."
  elif v==-1:
    print "The format of the web page source may have changed!"
  else:
    print "Price at time "+v[0]+": "+v[1]