A few days ago I blogged about my plans to make RSS Bandit a desktop client for Google Reader. As part of that process I needed to verify that it is possible to programmatically interact with Google Reader from a desktop client in a way that provides a reasonable user experience. To this end, I wrote a command line client in IronPython based on the documentation I found at the pyrfeed Website.

The command line client isn't terribly useful on its own as a way to read your feeds but it might be useful for other developers who are trying to interact with Google Reader programmatically who would learn better from  code samples than reverse engineered API documentation.

Enjoy...

PS: Note the complete lack of error handling. I never got a hang of error handling in Python let alone going back and forth between handling errors in Python vs. handling underlying .NET/CLR errors.


import sys
from System import *
from System.IO import *
from System.Net import *
from System.Text import *
from System.Globalization import DateTimeStyles
import clr
clr.AddReference("System.Xml")
from System.Xml import *
clr.AddReference("System.Web")
from System.Web import *

#################################################################
#
# USAGE: ipy greader.py <Gmail username> <password> <path-to-directory-for-storing-feeds>
# 
# username & password are required
# feed directory location is optional, defaults to C:\Windows\Temp\
#################################################################

#API URLs
auth_url          = rhttps://www.google.com/accounts/ClientLogin?continue=http://www.google.com&service=reader&source=Carnage4Life&Email=%s&Passwd=%s
feed_url_prefix   = rhttp://www.google.com/reader/atom/
api_url_prefix    = rhttp://www.google.com/reader/api/0/
feed_cache_prefix = r"C:\\Windows\Temp\\"
add_url           = r"http://www.google.com/reader/quickadd"

#enumerations
(add_label, remove_label) = range(1,3)

class TagList:
    """Represents a list of the labels/tags used in Google Reader"""
    def __init__(self, userid, labels):
        self.userid = userid
        self.labels = labels

class SubscriptionList:
    """Represents a list of RSS feeds subscriptions"""
    def __init__(self, modified, feeds):
        self.modified = modified
        self.feeds    = feeds

class Subscription:
    """Represents an RSS feed subscription"""
    def __init__(self, feedid, title, categories, firstitemmsec):
        self.feedid        = feedid
        self.title         = title
        self.categories    = categories
        self.firstitemmsec = firstitemmsec

def MakeHttpPostRequest(url, params, sid):
    """Performs an HTTP POST request to a Google service and returns the results in a HttpWebResponse object"""
    req = HttpWebRequest.Create(url)
    req.Method = "POST"
    SetGoogleCookie(req, sid)

    encoding = ASCIIEncoding();
    data     = encoding.GetBytes(params)

    req.ContentType="application/x-www-form-urlencoded"
    req.ContentLength = data.Length
    newStream=req.GetRequestStream()
    newStream.Write(data,0,data.Length)
    newStream.Close()
    resp = req.GetResponse()
    return resp

def MakeHttpGetRequest(url, sid):
    """Performs an HTTP GET request to a Google service and returns the results in an XmlDocument"""
    req          = HttpWebRequest.Create(url)
    SetGoogleCookie(req, sid)
    reader = StreamReader(req.GetResponse().GetResponseStream())
    doc          = XmlDocument()
    doc.LoadXml(reader.ReadToEnd())
    return doc

def GetToken(sid):
    """Gets an edit token which is needed for any edit operations using the Google Reader API"""
    token_url = api_url_prefix + "token"
    req          = HttpWebRequest.Create(token_url)
    SetGoogleCookie(req, sid)
    reader = StreamReader(req.GetResponse().GetResponseStream())
    return reader.ReadToEnd()

def MakeSubscription(xmlNode):
    """Creates a Subscription class out of an XmlNode that was obtained from the feed list"""
    id_node     = xmlNode.SelectSingleNode("string[@name='id']")
    feedid      = id_node and id_node.InnerText or ''
    title_node  = xmlNode.SelectSingleNode("string[@name='title']")
    title       = title_node and title_node.InnerText or ''
    fim_node    =  xmlNode.SelectSingleNode("string[@name='firstitemmsec']")
    firstitemmsec = fim_node and fim_node.InnerText or ''
    categories  = [MakeCategory(catNode) for catNode in xmlNode.SelectNodes("list[@name='categories']/object")]
    return Subscription(feedid, title, categories, firstitemmsec)

def MakeCategory(catNode):
    """Returns a tuple of (label, category id) from an XmlNode representing a feed's labels that was obtained from the feed list"""
    id_node     = catNode.SelectSingleNode("string[@name='id']")
    catid       = id_node and id_node.InnerText or ''
    label_node  = catNode.SelectSingleNode("string[@name='label']")
    label       = label_node and label_node.InnerText or ''
    return (label, catid)

def AuthenticateUser(username, password):
    """Authenticates the user and returns a username/password combination"""
    req = HttpWebRequest.Create(auth_url % (username, password))
    reader = StreamReader(req.GetResponse().GetResponseStream())
    response = reader.ReadToEnd().split('\n')
    for s in response:
        if s.startswith("SID="):
            return s[4:]

def SetGoogleCookie(webRequest, sid):
    """Sets the Google authentication cookie on the HttpWebRequest instance"""
    cookie = Cookie("SID", sid, "/", ".google.com")
    cookie.Expires = DateTime.Now + TimeSpan(7,0,0,0)
    container      = CookieContainer()
    container.Add(cookie)
    webRequest.CookieContainer = container

def GetSubscriptionList(feedlist, sid):
    """Gets the users list of subscriptions"""
    feedlist_url = api_url_prefix + "subscription/list"
    #download the JSON-esque XML feed list
    doc = MakeHttpGetRequest(feedlist_url, sid)

    #create subscription nodes
    feedlist.feeds  = [MakeSubscription(node) for node in doc.SelectNodes("/object/list[@name='subscriptions']/object")]
    feedlist.modified = False

def GetTagList(sid):
  """Gets a list of the user's tags"""
  taglist_url = api_url_prefix + "tag/list"
  doc = MakeHttpGetRequest(taglist_url, sid)
  #get the user id needed for creating new labels from Google system tags

  userid = doc.SelectSingleNode("/object/list/object/string[contains(string(.), 'state/com.google/starred')]").InnerText
  userid = userid.replace("/state/com.google/starred", "");
  userid = userid[5:]
  #get the user-defined labels
  tags = [node.InnerText.Replace("user/" + userid + "/label/" ,"") for node in doc.SelectNodes("/object/list[@name='tags']/object/string[@name='id']") if node.InnerText.IndexOf( "/com.google/") == -1 ]
  return TagList(userid, tags)

def DownloadFeeds(feedlist, sid):
    """Downloads each feed from the subscription list to a local directory"""
    for feedinfo in feedlist.feeds:
        unixepoch  = DateTime(1970, 1,1, 0,0,0,0, DateTimeKind.Utc)
        oneweek_ago   = DateTime.Now - TimeSpan(7,0,0,0)
        ifmodifiedsince = oneweek_ago - unixepoch
        feed_url = feed_url_prefix + feedinfo.feedid +  "?n=25&r=o&ot=" + str(int(ifmodifiedsince.TotalSeconds))
        continuation = True
        continuation_token = ''
        feedDoc      = None

        while True:
            print "Downloading feed at %s" % (feed_url  + continuation_token)
            doc = MakeHttpGetRequest(feed_url + continuation_token, sid)
            continuation_node     = doc.SelectSingleNode("//*[local-name()='continuation']")
            continuation_token    = continuation_node and ("&c=" + continuation_node.InnerText) or ''

            if feedDoc is None:
                feedDoc = doc
            else:
                for node in doc.SelectNodes("//*[local-name()='entry']"):
                    node = feedDoc.ImportNode(node, True)
                    feedDoc.DocumentElement.AppendChild(node)

            if continuation_token == '':
                break

        print "Saving %s" % (feed_cache_prefix + feedinfo.title + ".xml")
        feedDoc.Save(feed_cache_prefix + feedinfo.title + ".xml")

def ShowSubscriptionList(feedlist, sid):
    """Displays the users list of subscriptions including the labels applied to each item"""
    if feedlist.modified:
        GetSubscriptionList(feedlist, sid)
    count = 1
    for feedinfo in feedlist.feeds:
        print "%s. %s (%s)" % (count, feedinfo.title, [category[0] for category in feedinfo.categories])
        count = count + 1

def Subscribe(url, sid):
    """Subscribes to the specified feed URL in Google Reader"""
    params        = "quickadd=" + HttpUtility.UrlEncode(url) + "&T=" + GetToken(sid)
    resp = MakeHttpPostRequest(add_url, params, sid)

    if resp.StatusCode == HttpStatusCode.OK:
        print "%s successfully added to subscription list" % url
        return True
    else:
        print resp.StatusDescription
        return False

def Unsubscribe(index, feedlist, sid):
    """Unsubscribes from the feed at the specified index in the feed list"""
    unsubscribe_url = api_url_prefix + "subscription/edit"
    feed = feedlist.feeds[index]
    params = "ac=unsubscribe&i=null&T=" + GetToken(sid) + "&t=" + feed.title  + "&s=" + feed.feedid
    resp = MakeHttpPostRequest(unsubscribe_url, params, sid)

    if resp.StatusCode == HttpStatusCode.OK:
        print "'%s' successfully removed from subscription list" % feed.title
        return True
    else:
        print resp.StatusDescription
        return False

def Rename(new_title, index, feedlist, sid):
    """Renames the feed at the specified index in the feed list"""
    api_url = api_url_prefix + "subscription/edit"
    feed = feedlist.feeds[index]
    params = "ac=edit&i=null&T=" + GetToken(sid) + "&t=" + new_title  + "&s=" + feed.feedid
    resp = MakeHttpPostRequest(api_url, params, sid)

    if resp.StatusCode == HttpStatusCode.OK:
        print "'%s' successfully renamed to '%s'" % (feed.title, new_title)
        return True
    else:
        print resp.StatusDescription
        return False

def EditLabel(label, editmode, userid, feedlist, index, sid):
    """Adds or removes the specified label to the feed at the specified index depending on the edit mode"""
    full_label = "user/" + userid + "/label/" + label
    label_url = api_url_prefix + "subscription/edit"
    feed = feedlist.feeds[index]
    params = "ac=edit&i=null&T=" + GetToken(sid) + "&t=" + feed.title  + "&s=" + feed.feedid

    if editmode == add_label:
        params = params + "&a=" + full_label
    elif editmode == remove_label:
        params = params + "&r=" + full_label
    else:
        return

    resp = MakeHttpPostRequest(label_url, params, sid)
    if resp.StatusCode == HttpStatusCode.OK:
        print "Successfully edited label '%s' of feed '%s'" % (label, feed.title)
        return True
    else:
        print resp.StatusDescription
        return False

def MarkAllItemsAsRead(index, feedlist, sid):
    """Marks all items from the selected feed as read"""
    unixepoch  = DateTime(1970, 1,1, 0,0,0,0, DateTimeKind.Utc)

    markread_url = api_url_prefix + "mark-all-as-read"
    feed = feedlist.feeds[index]
    params = "s=" + feed.feedid + "&T=" + GetToken(sid) + "&ts=" + str(int((DateTime.Now - unixepoch).TotalSeconds))
    MakeHttpPostRequest(markread_url, params, sid)
    print "All items in '%s' have been marked as read" % feed.title

def GetFeedIndexFromUser(feedlist):
    """prompts the user for the index of the feed they are interested in and returns the index as the result of this function"""
    print "Enter the numeric position of the feed from 1 - %s" % (len(feedlist.feeds))
    index = int(sys.stdin.readline().strip())
    if (index < 1) or (index > len(feedlist.feeds)):
        print "Invalid index specified: %s" % feed2label_indx
        return -1
    else:
        return index

if __name__ == "__main__":
       if len(sys.argv) < 3:
           print "ERROR: Please specify a Gmail username and password"
       else:
           if len(sys.argv) > 3:
               feed_cache_prefix = sys.argv[3]

           SID = AuthenticateUser(sys.argv[1], sys.argv[2])
           feedlist = SubscriptionList(True, [])
           GetSubscriptionList(feedlist, SID)
           taglist = GetTagList(SID)

           options = "***Your options are (f)etch your feeds, (l)ist your subscriptions, (s)ubscribe to a new feed, (u)nsubscribe, (m)ark read , (r)ename, (a)dd a label to a feed, (d)elete a label from a feed or (e)xit***"
           print "\n"

           while True:
               print options
               cmd = sys.stdin.readline()
               if cmd == "e\n":
                   break
               elif cmd == "l\n": #list subscriptions
                   ShowSubscriptionList(feedlist, SID)
               elif cmd == "s\n": #subscribe to a new feed
                   print "Enter url: "
                   new_feed_url = sys.stdin.readline().strip()
                   success = Subscribe(new_feed_url, SID)

                   if feedlist.modified == False:
                       feedlist.modified = success
               elif cmd == "u\n": #unsubscribe from a feed
                   feed2remove_indx = GetFeedIndexFromUser(feedlist)
                   if feed2remove_indx != -1:
                       success = Unsubscribe(feed2remove_indx-1, feedlist, SID)

                       if feedlist.modified == False:
                           feedlist.modified = success
               elif cmd == "r\n": #rename a feed
                   feed2rename_indx = GetFeedIndexFromUser(feedlist)
                   if feed2rename_indx != -1:
                       print "'%s' selected" % feedlist.feeds[feed2rename_indx -1].title
                       print "Enter the new title for the subscription:"
                       success = Rename(sys.stdin.readline().strip(), feed2rename_indx-1, feedlist, SID)

                       if feedlist.modified == False:
                           feedlist.modified = success
               elif cmd == "f\n": #fetch feeds
                   feedlist = DownloadFeeds(feedlist, SID)
               elif cmd == "m\n": #mark all items as read
                   feed2markread_indx = GetFeedIndexFromUser(feedlist)
                   if feed2markread_indx != -1:
                       MarkAllItemsAsRead(feed2markread_indx-1, feedlist, SID)
               elif (cmd == "a\n") or (cmd == "d\n"): #add/remove a label on a feed
                   editmode = (cmd == "a\n") and add_label or remove_label
                   feed2label_indx = GetFeedIndexFromUser(feedlist)
                   if feed2label_indx != -1:
                       feed = feedlist.feeds[feed2label_indx-1]
                       print "'%s' selected" % feed.title
                       print "%s" % ((cmd == "a\n") and "Enter the new label:" or "Enter the label to delete:")
                       label_name = sys.stdin.readline().strip()
                       success = EditLabel(label_name, editmode, taglist.userid, feedlist, feed2label_indx-1, SID)

                       if feedlist.modified == False:
                           feedlist.modified = success
               else:
                   print "Unknown command"

Now Playing: DJ Drama - Cannon (Remix) (Feat. Lil Wayne, Willie The Kid, Freeway And T.I.)


 

Monday, December 31, 2007 1:51:15 PM (GMT Standard Time, UTC+00:00)
Wow - this is cool.

Not sure why you have a problem with Python's exception handling - it is very similar to C# (except less curly braces of course).
Monday, December 31, 2007 2:15:00 PM (GMT Standard Time, UTC+00:00)
Thanks for sharing code, and not just pseudocode.

But can you consider just linking to a codepaste site or a link to an external file next time? My feed reader nearly had a coronary.

Also, can you elaborate on how you find Python's exception handling confusing? I'd be happy to offer any insights I've got (I've been coding Python, on and off, for ~7 years.)
Monday, December 31, 2007 3:53:23 PM (GMT Standard Time, UTC+00:00)
"My feed reader nearly had a coronary."

Mine did too! Every word in that code was in a new line of its own.
Dilip
Monday, December 31, 2007 5:28:17 PM (GMT Standard Time, UTC+00:00)
Joe and Michael,
I haven't found good tutorials on exception handling in Python online. What makes the situation more complicated is that the majority of the exceptions I want to handle are thrown by .NET libraries (e.g. HttpWebRequest) and I've found nothing on how to do that online.

I must be using the wrong keywords in my searches. :)
Monday, December 31, 2007 7:19:10 PM (GMT Standard Time, UTC+00:00)
Dare, what did you use to format and colorize the code here. It comes through really ugly in RSS bandit. I haven't looked at the source but I wonder if you are using LiveWriter (which does not seem to know how to handle *pre* tags. (By the way, I hate your HTML filter. Rather than treating it as text, it objects to use of what might look like HTML, so I can't even *talk* about HTML in a comment here.)

I haven't found a plug-in that I can stand to use yet. I like your result on the blog page, but I would really like to see the RSS feed be presented properly too. Any ideas?
Monday, December 31, 2007 7:54:41 PM (GMT Standard Time, UTC+00:00)
orcmid,
It looks like the problem is with Windows Live Writer. It looks like I'll have to go back to Blogjet.
Tuesday, January 1, 2008 12:51:18 PM (GMT Standard Time, UTC+00:00)
Hi Dare,

The reason that there isn't much discussion of catching .NET exceptions from IronPython - is that it is exactly the same as catching the Python exceptions from IronPython...

You can just import the exception names and use them in your except/finally blocks.

Michael
Comments are closed.