Help with Python GTK.

Hi, I'm trying to learn how to program so I'm really new to this and I thought python would be good because it seemed simple and its cross platform, so I was watching a tutorial on YouTube for making a window.
Heres the code

Code:

#!/usr/bin/env Python

import pygtk
pygtk.require('2.0')
import gtk

class Base:
    def __init__(self):
        self.Window = gtk.Window(gtk.WINDOW_TOPLEVEL)
        self.Window.show()

    def main(self):
        gtk.main()
        
if __name__ == "__main__":
    base = Base()
    base.main()

When I try to run it it says 'No module named pygtk' I'm used Text Wrangler for it and got that result but if I write it in Terminal I get basically the same thing. So I'm wondering how would I have it find the pygtk, or not need it?