pygtk is provided by python-gobject. gtk is provided by python-gtk2.
The pygtk library provides the pygtk.require function which gives you the option to require that a certain version of gtk (or better) is installed.
For example:
import pygtk
pygtk.require('2.0')
Importing gtk only is possible, but your program may not work as expected on someone else’s machine if their version of gtk is older.
So pygtk is used only to require that a certain version of gtk is installed ?
Yes. If you open a terminal, and type:
python >>> import pygtk >>> pygtk.__file__
You’ll find the path to the package. It might be something like /usr/lib/pymodules/python2.6/pygtk.pyc. If you take the c off the end of the path, and look inside the file /usr/lib/pymodules/python2.6/pygtk.py you’ll find it defines just three functions, and they all have to do with determining and requiring versions.