It depends (doesn't that always suck?).

If you installed pygtk to a non-standard directory (i.e., not in your python installation's site-packages directory), you will need to manually set pythonpath accordingly, and take care of python versions youself (checking pygtk_version, for instance). If you installed it into a standard directory, read below.

We have now a concept of a `default pygtk version'. This is the version that you get if you do a simple 'import gtk' in Python. Precisely which is the default version varies:

• If you are using a dual-install version of pygtk (faq 2.5) it depends on the contents of a file called pygtk.pth, which is installed into the python site-packages directory. It's written there by the pygtk source tarball's `make install' target, so if you compile and install pygtk2 after pygtk0 the default will be pygtk2 and vice-versa.
• If you are using an older version of pygtk, you will need to check pygtk_version yourself, noting that you won't be able to select versions using the pygtk module.

To *make sure* you get the right version, you can use:

  import pygtk
  pygtk.require("1.2") # or 2.0 etc

Which I recommend for maximum cross-site functionality. HOWEVER, not all versions of pygtk offer the pygtk module (again, see faq 2.5). So to do the right thing, you need to wrap that in a try/except clause, and use a check for the previous versions. Something like the following should work if you want to make sure you have version 1.2:

 # Make sure we have version 1.2. Swap for 2.0 as necessary.

 def get_gtk():
   print """You need to get version 0.6 of PyGTK for this to work. You 
            can get source code from http://ftp.gnome.org/pub/gimp/gtk/python/v1.2/ """
   raise SystemExit

 try:
   import pygtk
   pygtk.require("1.2")
 except ImportError:
   try:
     import gtk   
   except ImportError:
     get_pygtk()
   if not hasattr(gtk, "GtkWindow"): # renamed in version 2.0
     get_pygtk()
 except AssertionError:
   get_pygtk()

  import gtk # we KNOW this is 1.2 at this point
  [...]

[The whole pygtk.pth handling has shown itself to be something of a mess, unfortunately, and a separate gtk2 namespace might have saved us some trouble, IMHO. - Kiko]