itertools.chain链接一个iter列表？

import itertools
def _yield_sample():
    it = iter(itertools.combinations('ABCD', 2))
    it2 = iter(itertools.combinations('EFGH', 3))
    itc = itertools.chain(it,it2)
    for x in itc:
        yield x

def main():
    for x in _yield_sample():
        print x

>>> 
('A', 'B')
('A', 'C')
('A', 'D')
...

def __position_combination(_count = [2,3,4,5]):
    its = []
    for ct in _count:
        it = iter(itertools.combinations('ABCDEFG', ct))
        its.append(it)
    itc = itertools.chain(its)
    for x in itc:
        yield x

def main():
    for x in __position_combination():
        print x

>>> 
<itertools.combinations object at 0x02179210>
<itertools.combinations object at 0x02179240>
<itertools.combinations object at 0x02179270>

itc = itertools.chain(*its)

itertools.chain(iter, iter, iter)  vs    itertools.chain(*[iter,iter,iter])

itertools.chain

def chain(*iterables):
    # chain('ABC', 'DEF') --> A B C D E F
    for it in iterables:
        for element in it:
            yield element

itertools.chain(iter, iter, iter)

iter, iter, iter = *(iter, iter, iter)