itertools.chain链接一个iter列表？

Question

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

这适用于打印组合.

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

但是这个:

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

不会,它会打印出来

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

我必须重写代码以使其按要求工作.

itc = itertools.chain(*its)

这是我的问题:

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

他们之间有什么不同？根据文档 的itertools.chain作用:

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

那么,为什么itertools.chain(iter, iter, iter)这里也有效呢？
这意味着iter, iter, iter = *(iter, iter, iter)什么？

Answer 1

是.

但是itertools.chain.from_iterable().