okay...

test.py

#!/usr/bin/python
from gi.repository import Gtk, GdkPixbuf

# this will be a twitter thing and objects will be created there of course
class Account():
	def __init__(self, avatar, handle):
		self.avatar = avatar
		self.handle = handle
		# other things

a1 = Account("./icon.png", "@alliepaca")
a2 = Account("./icon.png", "Another account")

class Tweet():
	def __init__(self):
		self.icon = GdkPixbuf.Pixbuf.new_from_file_at_size("./icon.png", 20,20)
		self.name = "allie"
		self.user = "@alliepaca"
		self.message = "testing 1 2 3"
		self.date = "00:44"

class SidebarTree(Gtk.TreeView):
	def __init__(self):
		Gtk.TreeView.__init__(self)
		self.set_model(Gtk.TreeStore(GdkPixbuf.Pixbuf, str))

	def add_account(self, account):
		model = self.get_model()
		icon = GdkPixbuf.Pixbuf.new_from_file_at_size(account.avatar, 20,20)
		a = model.append(None, [icon, account.handle])
		model.append(a, [None, "Timeline"])
		model.append(a, [None, "Notifications"])
		model.append(a, [None, "Messages"])

class AccountsColumn(Gtk.TreeViewColumn):
	def __init__(self):
		Gtk.TreeViewColumn.__init__(self, "Accounts")
		accicon = Gtk.CellRendererPixbuf()
		accounts = Gtk.CellRendererText()
		self.pack_start(accicon, False)
		self.pack_start(accounts, False)
		self.add_attribute(accicon, "pixbuf", 0)
		self.add_attribute(accounts, "text", 1)

class FromColumn(Gtk.TreeViewColumn):
	def __init__(self):
		Gtk.TreeViewColumn.__init__(self, "From")
		r_icon = Gtk.CellRendererPixbuf()
		r_from = Gtk.CellRendererText()
		r_handle = Gtk.CellRendererText()
		r_from.set_property("weight", 600)
		r_handle.set_property("foreground", "#A0A0A0")
		self.pack_start(r_icon, False)
		self.pack_start(r_from, False)
		self.pack_start(r_handle, False)
		self.add_attribute(r_icon, "pixbuf", 0)
		self.add_attribute(r_from, "text", 1)
		self.add_attribute(r_handle, "text", 2)

class MessageColumn(Gtk.TreeViewColumn):
	def __init__(self):
		Gtk.TreeViewColumn.__init__(self, "Message")
		self.set_expand(True)
		r_text = Gtk.CellRendererText()
		#r_text.set_property("yalign", 0)
		self.pack_start(r_text, True)
		self.add_attribute(r_text, "text", 3)

class TimeColumn(Gtk.TreeViewColumn):
	def __init__(self):
		Gtk.TreeViewColumn.__init__(self, "Time")
		r_time = Gtk.CellRendererText()
		#r_time.set_property("yalign", 0)
		self.pack_start(r_time, True)
		self.add_attribute(r_time, "text", 4)

class TweetsTree(Gtk.TreeView):
	def __init__(self):
		Gtk.TreeView.__init__(self)
		self.set_model(Gtk.ListStore(GdkPixbuf.Pixbuf, str, str, str, str))
		self.set_rules_hint(True)

	def add_tweet(self, tweet):
		model = self.get_model()
		model.prepend([tweet.icon, tweet.name, tweet.user, tweet.message, tweet.date])


class MainWindow(Gtk.Window):
	def __init__(self):
		Gtk.Window.__init__(self, title="bird")
		self.connect("delete-event", Gtk.main_quit)
		self.set_default_size(1280, 720)

		# Horizontal splitter
		self.main_pane = Gtk.Paned()
		self.main_pane.set_orientation(Gtk.Orientation.HORIZONTAL)
		self.main_pane.set_position(200)
		self.add(self.main_pane)

		# Vertical splitter
		self.secondary_pane = Gtk.Paned()
		self.secondary_pane.set_orientation(Gtk.Orientation.VERTICAL)
		self.secondary_pane.set_position(300)
		self.main_pane.add2(self.secondary_pane)

		# Sidebar tree
		self.sidebar = SidebarTree()
		self.sidebar.add_account(a1)
		self.sidebar.add_account(a2)

		self.main_pane.add1(self.sidebar)

		self.sidebar.append_column(AccountsColumn())

		self.sidebar.expand_all()

		# Main tweet list
		self.tweets = TweetsTree()
		self.secondary_pane.add(self.tweets)
		self.tweets.append_column(FromColumn())
		self.tweets.append_column(MessageColumn())
		self.tweets.append_column(TimeColumn())


	def add_tweet(self, tweet):
		self.tweets_store.prepend([tweet.icon, tweet.name, tweet.user, tweet.message, tweet.date])

class Tweet():
	def __init__(self):
		self.icon = GdkPixbuf.Pixbuf.new_from_file_at_size("./icon.png", 20,20)
		self.name = "allie"
		self.user = "@alliepaca"
		self.message = "testing 1 2 3"
		self.date = "00:44"


win = MainWindow()
win.show_all()
Gtk.main()