How to sort tree view on click on column header

Enjoy!

#! /usr/bin/python

###########################################################
#
# Basic Gtk.TreeView Example with two sortable columns
#
###########################################################


# use  the new PyGObject binding
from gi.repository import Gtk
import os
import getpass # this is only to automatically print your home folder.

class MyWindow(Gtk.Window):

    def __init__(self):
        Gtk.Window.__init__(self, title='My Window Title')
        self.connect('delete-event', Gtk.main_quit)        

        # Gtk.ListStore will hold data for the TreeView
        # Only the first two columns will be displayed
        # The third one is for sorting file sizes as numbers

        store = Gtk.ListStore(str, str, long)

        # Get the data - see below
        self.populate_store(store)

        treeview = Gtk.TreeView(model=store)

        # The first TreeView column displays the data from
        # the first ListStore column (text=0), which contains
        # file names
        renderer_1 = Gtk.CellRendererText()        
        column_1 = Gtk.TreeViewColumn('File Name', renderer_1, text=0)

        # Calling set_sort_column_id makes the treeViewColumn sortable
        # by clicking on its header. The column is sorted by
        # the ListStore column index passed to it 
        # (in this case 0 - the first ListStore column) 
        column_1.set_sort_column_id(0)        
        treeview.append_column(column_1)

        # xalign=1 right-aligns the file sizes in the second column
        renderer_2 = Gtk.CellRendererText(xalign=1)

        # text=1 pulls the data from the second ListStore column
        # which contains filesizes in bytes formatted as strings
        # with thousand separators
        column_2 = Gtk.TreeViewColumn('Size in bytes', renderer_2, text=1)

        # Make the Treeview column sortable by the third ListStore column
        # which contains the actual file sizes
        column_2.set_sort_column_id(1)
        treeview.append_column(column_2)

        # Use ScrolledWindow to make the TreeView scrollable
        # Otherwise the TreeView would expand to show all items
        # Only allow vertical scrollbar
        scrolled_window = Gtk.ScrolledWindow()
        scrolled_window.set_policy(Gtk.PolicyType.NEVER, Gtk.PolicyType.AUTOMATIC)
        scrolled_window.add(treeview)
        scrolled_window.set_min_content_height(200)

        self.add(scrolled_window)
        self.show_all()

    def populate_store(self, store):            
        directory = '/home/'+getpass.getuser()
        for filename in os.listdir(directory):
            size = os.path.getsize(os.path.join(directory, filename))
            # the second element is displayed in the second TreeView column
            # but that column is sorted by the third element
                # so the file sizes are sorted as numbers, not as strings
                store.append([filename, '{0:,}'.format(size), size])       

    # The main part:
    win = MyWindow()
    Gtk.main()

In order:

1. You really need to start looking more at the fine documentation.
2. Make sure you set a sort column id on each of your columns, then look at the GtkTreeSortable interface. This tutorial section is helpful, too.
3. Set the "xalign" property of your GtkCellRenderer to 0.f.