some questions about Python and tkinter

[fabdeb]

Hi every one,
I m a sysadmin who want to know how to use python.
I dont know anything about oriented object programation, i only know
bash and a little perl.
I have some simple questions about python.

the first: what is the differences between a function and a classe?

In which case i should use a function ?
In which case i should use a class ?

The second: there is some pincipals gui toolkit: tkinter , Python Mega-
Widgets, PyGTK, PyQt, FxPy, WxPy

what are the advantages of each one, and in which case i use each of
them?

thanks by advance,

Fabrice.witkowski