Postcode validation using GJS or PyGObject

postcode.js

#!/usr/bin/gjs

const Gtk = imports.gi.Gtk;
const Lang = imports.lang;

var re = /[A-Z]{1,2}[\d][A-Z0-9]? ?[\d][A-Z]{2}/

const Postcode = new Lang.Class(
{
    Name: 'Postcode',

    _init: function()
    {
        this.application = new Gtk.Application();
        this.application.connect('activate', Lang.bind(this, this._onActivate));
        this.application.connect('startup', Lang.bind(this, this._onStartup));
    },

    _onActivate: function()
    {
        this._window.show_all();
    },

    _onStartup: function()
    {
        this._window = new Gtk.ApplicationWindow({ application: this.application,
                                                   title: "Postcode",
                                                   window_position: Gtk.WindowPosition.CENTER });

        let entry = new Gtk.Entry({ secondary_icon_tooltip_text: "Not a valid postcode" });
        entry.connect('changed', Lang.bind(this, this._onChanged));
        this._window.add(entry);
    },

    _onChanged: function(editable)
    {
        let text = editable.get_chars(0, -1);

        if (!text)
        {
            editable.secondary_icon_name = null;
            return;
        }

        if (re.test(text))
            editable.secondary_icon_name = null;
        else
            editable.secondary_icon_name = "dialog-warning-symbolic";
    }
});

let app = new Postcode();
app.application.run(ARGV);

postcode.py

#!/usr/bin/env python

import re

from gi.repository import Gtk

class Postcode(Gtk.Window):
	def __init__(self):
		Gtk.Window.__init__(self)
		self.set_title("Postcode")
		self.connect("destroy", lambda w: Gtk.main_quit())

		self.entry = Gtk.Entry()
		self.entry.connect("changed", self._on_entry_changed)
		self.entry.set_icon_tooltip_text(Gtk.EntryIconPosition.SECONDARY, "Not a valid postcode")
		self.add(self.entry)

		self.regex = re.compile("[A-Z]{1,2}[0-9][A-Z0-9]? ?[0-9][A-Z]{2}")

	def _on_entry_changed(self, editable):
		text = editable.get_chars(0, -1)
		result = self.regex.match(text)

		if text == "":
			editable.set_icon_from_icon_name(Gtk.EntryIconPosition.SECONDARY, None)
		else:
			if result == None:
				editable.set_icon_from_icon_name(Gtk.EntryIconPosition.SECONDARY, "dialog-warning-symbolic")
			else:
				editable.set_icon_from_icon_name(Gtk.EntryIconPosition.SECONDARY, None)

if __name__ == "__main__":
	postcode = Postcode()

	postcode.connect("destroy", lambda w: Gtk.main_quit())
	postcode.show_all()

	Gtk.main()