lambo@multivac:~> python
Python 2.7.3 (default, Jul  3 2012, 21:16:07) 
[GCC 4.7.1] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import gtk
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named gtk
>>>

root@multivac:~> slackpkg search py

Looking for py in package list. Please wait... DONE

The list below shows all packages with name matching "py".

[uninstalled] - floppy-5.4-i386-3
[ installed ] - python-2.7.3-i486-2
[uninstalled] - kfloppy-4.8.5-i486-1
[uninstalled] - pykde4-4.8.5-i486-1
[uninstalled] - dbus-python-1.1.0-i486-1
[uninstalled] - notify-python-0.1.1-i486-3
[uninstalled] - pycairo-1.8.10-i486-2
[uninstalled] - pycups-1.9.61-i486-1
[uninstalled] - pycurl-7.19.0-i486-2
[uninstalled] - pygobject-2.28.6-i486-2
[ installed ] - pygtk-2.24.0-i486-1
[uninstalled] - pyrex-0.9.9-i486-2
[ installed ] - xdpyinfo-1.3.0-i486-1
[ installed ] - xpyb-1.3.1-i486-2

You can search specific files using "slackpkg file-search file".

root@multivac:~> slackpkg search gtk

Looking for gtk in package list. Please wait... DONE

The list below shows all packages with name matching "gtk".

[uninstalled] - oxygen-gtk2-1.3.0-i486-1
[uninstalled] - gtk+-1.2.10-i486-5
[ installed ] - gtk+2-2.24.10-i486-2
[uninstalled ] - gtk+3-3.4.4-i486-1
[uninstalled] - gtkspell-2.0.16-i486-1
[ installed ] - pygtk-2.24.0-i486-1
[uninstalled] - gtk-xfce-engine-3.0.0-i486-1

You can search specific files using "slackpkg file-search file".