Simple Newbie Question: What am I doing wrong?

[MDK]

I have a file named mytest.py containing the following:

def yo():
    print "Bla"


In the interactive window I type:

>>> import mytest
>>> mytest.yo

But I get back

<function yo at 0x00985378>

Why don't I get back "Bla"?

Neither does it work if I do:

   return "Bla"

Why not?

Thank you for your help.