def test_first(self):
lst = ['A', 'B', 'C', 'D']
self.assertTrue(iterators.first(lst) == 'A')
gen = range(20, 30)
self.assertTrue(iterators.first(gen) == 20)
self.assertTrue(iterators.first([], None) == None)
self.assertTrue(iterators.first([], 'poo') == 'poo')
self.assertRaises(StopIteration, iterators.first, [])
def scan(func, sequence, init=None):
if init is None:
curr = first(sequence)
else:
curr = init
yield init
for element in sequence:
curr = func(curr, element)
yield curr