Style/efficiency question using 'in'

[Nick Belshaw]

If someone could spare a mo to clarify -

If I do something like :-

------------------
def  func1():
    return 1,2,3,4,5,6,7,8

for x in func1():
    print x
------------------

it works as expected but is the use of a function in a loop undesirable?
Is the function called once to build the loop or is it called each loop
increment and therefore undesirable if there is much overhead?

greatful for any comments

cheers
Nick/Oxford