any trick to allow anonymous code blocks in python?

[Doug Holton]

Is there any metaclass trick or something similar to allow anonymous 
code blocks?

I'd like to be able to let users do something like this fictitious example:
b = Button()
b.OnClick =:
     print "you clicked me"

But that would require adding a special "=:" operator to bind a code 
block to a function.
Is there any PEP for something like that?  I see 310 might allow:
b=Button()
with b.OnClick:
     print "you clicked me"

I know I can already do it like these examples:
def OnClick(self,event):
     print "you clicked me"
b.OnClick = OnClick
or
b = Button(OnClick=OnClick)
or subclassing Button.