Un widget que crea un a especie de combobox solo que en vers de desplegar una lista, desplega un calendario.

gistfile1.py

#!/usr/bin/python
# -*- coding: UTF-8 -*-
# vim: ai ts=4 sts=4 et sw=4
# Autor: Hector Miuler Malpica Gallegos
# Email: miuler@gmail.com
# Rev: $Rev
# -------------------------------------------------------------------                                                          

import gtk
import datetime

class Window:
    
    def __init__(self):
        win = gtk.Window()
        win.set_title('Prueba de Comobobox + Calendar')
        win.connect('destroy', gtk.main_quit)
        
        cmb = ComboBoxCalendar(win)
        label = gtk.Label('Miuler')
        vbox = gtk.VBox()
        vbox.pack_start(label)
        vbox.pack_start(cmb)

        win.add(vbox)
        win.show_all()
        gtk.main()

class ComboBoxCalendar(gtk.HBox):
    
    def __init__(self, window, *argv):
        super(ComboBoxCalendar, self).__init__(*argv)
        self._window = window
        self.entry = gtk.Entry()
        self.button = gtk.Button('V')

        #self.entry.connect('key-press-event', self.on_key_or_button_press)
        #self.entry.connect('button-press-event', self.on_key_or_button_press)
        self.button.connect('clicked', self.on_button)

        self.pack_start(self.entry, 0, 0)
        self.pack_start(self.button, 0, 0)

    def on_key_or_button_press(self, entry, event):
        self.button.clicked()

    def on_button(self, button):
        #$win_pos=$this->parent_window->get_position();
        win_position = self.window.get_position()
        x_field_pos = self.entry.allocation.x
        y_field_pos = self.entry.allocation.y
        x_shift = 0
        y_shift = 0 + self.entry.allocation.height

        x_win = win_position[0] + x_field_pos + x_shift
        y_win = win_position[1] + y_field_pos + y_shift

        self.dialog = gtk.Dialog(None, None,
            gtk.DIALOG_MODAL|gtk.DIALOG_NO_SEPARATOR)
        self.dialog.set_decorated(False)
        self.dialog.set_uposition(x_win, y_win)

        calendar = gtk.Calendar()
        calendar.show()
        self.dialog.vbox.pack_start(calendar, 0, 0)

        #calendar.connect('day-selected', self.on_select)
        #calendar.connect('month-changed', self.on_select)
        #self.dialog.connect('button-press-event', self.on_buttonpress)
        self.dialog.add_button(gtk.STOCK_APPLY, gtk.RESPONSE_ACCEPT)
        if self.dialog.run() == gtk.RESPONSE_ACCEPT:
            self.date = datetime.date(*calendar.get_date())
            self.entry.set_text(str(self.date))
        self.dialog.destroy()


Window()