python-3.x - 生成器函数在各种迭代上下文中的行为不同

Question

所以我有这个用于非递归排列的生成器函数，当我在 for 循环中使用它时，我得到了我期望的结果:

>>> for p in permutate3( "abc" ): print( p )
...
['a', 'b', 'c']
['a', 'c', 'b']
['b', 'a', 'c']
['b', 'c', 'a']
['c', 'a', 'b']
['c', 'b', 'a']

但是一旦我在列表中使用它或使用参数解包打印我得到这个奇怪的输出:

>>> list( permutate3( "abc" ) )
[['c', 'b', 'a'], ['c', 'b', 'a'], ['c', 'b', 'a'], ['c', 'b', 'a'], ['c', 'b', 'a'], ['c', 'b', 'a']]
>>> print( *permutate3( "abc" ) )
['c', 'b', 'a'] ['c', 'b', 'a'] ['c', 'b', 'a'] ['c', 'b', 'a'] ['c', 'b', 'a'] ['c', 'b', 'a']

为什么会这样？..

函数本身是:

def permutate3( s ):
    l = len( s )
    taken = [ False ] * l
    permutation = [ None ] * l
    current = 0
    stack = [ 0 ]

    while True:
        while stack[-1] < l:
            if not taken[ stack[-1] ]:
                permutation[current] = s[ stack[-1] ]
                if current == l-1:
                    yield permutation
                else:
                    taken[ stack[-1] ] = True
                    stack.append( 0 )
                    current+=1
                    break
            stack[-1]+=1
        else:
            stack.pop()
            if len( stack ) == 0:
                break
            else:
                current-=1
                taken[ stack[-1] ] = False
                stack[-1]+=1
                continue

Answer 1

假我。我的函数每次都产生对同一个对象的引用，该对象由函数更改以进行后续排列。显然应该是 yield list( permutation )。