python how to make your application check for updates

1import Tkinter
2import urllib
3
4def updateCheck(self):
5    update = False
6
7    updateWindow = Tkinter.Toplevel()
8    updateWindow.title(string="Update Checker")
9    updateWindow.resizable(False, False)
10
11    #Gets downloaded version
12    versionSource = open('version.txt', 'r')
13    versionContents = versionSource.read()
14
15    #gets newest version
16    updateSource = urllib.urlopen("http://www.suturesoft.com/Updates/craftbook.txt")
17    updateContents = updateSource.read()
18
19    #checks for updates
20    for i in range(0,20):
21        if updateContents[i] != versionContents[i]:
22            dataLabel = Tkinter.Label(updateWindow,text="\n\nThere are data updates availible.\n\n")
23            dataLabel.pack()
24            update = True
25            break
26    for i in range(22,42):
27        if updateContents[i] != versionContents[i]:
28            versionLabel = Tkinter.Label(updateWindow,text="\n\nThere are version updates availible.\n\n")
29            versionLabel.pack()
30            update = True
31            break
32    if update == False:
33        versionLabel = Tkinter.Label(updateWindow,text="\n\nYou are already running the most up to date version.\n\n")
34        versionLabel.pack()
35