Разделите список на основе условия
good, bad = [], []
for x in mylist:
(bad, good)[x in goodvals].append(x)
# good.append(x) if x in goodvals else bad.append(x)
# for x in mylist: (good if isgood(x) else bad).append(x)
# (good if x in goodvals else bad).append(x)
stuntbunny