[pygame] groups

["Gonzalo Castro" <gonzalo.castro.castilla@xxxxxxxxx>]

HI! I'm practising with groups and I have problems. ;)
I have 2 clases, ball and killer... they are more or less the same,
and 3 objects: a 2 of class ball and the other of class killer. I
grouped both of 2 objects balls into a group called my_balls. I define
it like this:

global my_balls= pygame.sprite.Group(ball, second)

and at  some point of the game I do:

print(myballs.has())

And this prints None. What Am I missing?

Thank you a lot. :)