short-circuiting any/all ?

kj no.email at please.post
Mon Mar 22 15:45:22 CET 2010




I have a list of items L, and a test function is_invalid that checks
the validity of each item.  To check that there are no invalid
items in L, I could check the value of any(map(is_invalid, L)).
But this approach is suboptimal in the sense that, no matter what
L is, is_invalid will be executed for all elements of L, even though
the value returned by any() is fully determined by the first True
in its argument.  In other words, all calls to is_invalid after
the first one to return True are superfluous.  Is there a
short-circuiting counterpart to any(map(is_invalid, L)) that avoids
these superfluous calls?

OK, there's this one, of course:

def _any_invalid(L):
    for i in L:
        if is_invalid(i):
            return True
    return False   

But is there anything built-in?  (I imagine that a lazy version of
map *may* do the trick, *if* any() will let it be lazy.)

TIA!

~K



More information about the Python-list mailing list