Subclassed: Notes on Google Finance API

11 October 2008

Notes on Google Finance API

I recently started dabbling in shares (yeah, I know, I like swimming against the flow), and so I looked around for good stock-price trackers for KDE3. To my surprise, I couldn't find anything apart from the usual KMyMoney (which I like and use, but it's not really something you can keep open all day on your desktop). I had already put my stock info on Google Finance, and lo, the service has a GData API, so I decided to write a small script in Python to retrieve my portfolio and the daily variations.

The good thing about GData APIs is that they are all the same at a basic level, so even when client libraries don't explicitly expose new features (like in this case, as Finance is quite a new service), you can still use the APIs to get easy authentication and feed-parsing. So I went and downloaded the official (and excellent) gdata-python-client package, which is dead-easy to use:

from gdata.service import GDataService

client = GDataService()
client.email = 'your_email@gmail.com'
client.password = 'your_password'
client.service = 'finance'

client.ProgrammaticLogin()

baseURL = "http://finance.google.com/finance/feeds/%(email)s/" % {'email':client.email}

# to get all data in one go:
#  bigFeed = client.GetFeed(baseURL + "portfolios?positions=true&returns=true")
# and then positionsFeed is included in each Entry
#  positionsFeed = gdata.GDataFeedFromString(bigfeed.entry[0].FindExtensions('feedLink')[0].children[0].ToString())

# ... but I really just want the first portfolio
positionsFeed = client.GetFeed(baseURL + "portfolios/1/positions?returns=true")

for entry in positionsFeed.entry:
 details = entry.FindExtensions('symbol')[0] 
 symbol = details.attributes['symbol']
 name = details.attributes['fullName']
 
 data = entry.FindExtensions('positionData')[0]
 totalReturn = round(float(data.attributes['returnOverall']) * 100,2)
 gainPerc = round(float(data.attributes['gainPercentage']) * 100,2)
 
 print name + " (" + symbol + ") Return: " + str(totalReturn) + "% - Gain: " + str(gainPerc) + "%"

One should really make an applet or something for KDE, but I'm leaving for Japan in about six hours so I can't be bothered...

Labels: foreverythingelsetherespython, GeekDiary, Google, GoogleFinance