生成器函数产生最大的可迭代值

Question

我是 python 的初学者，我目前正在为我的班级准备一个测试。我对一个问题的某一部分感到困惑。

我们被要求创建一个生成器函数，该函数仅在所有其他可迭代参数停止迭代后生成最大可迭代参数的结果。

所以，我的函数目前看起来是这样的：

def generator(*args):
    args = [iter(a) for a in args]
    while True:
        yielded = False
        for a in args:
            try:
                yield next(a)
                yielded = True
            except StopIteration:
                pass
        if not yielded:
            return
a = generator('abc', 'abcdef', [1,2])
print([i for i in a])

>>> ['a', 'a', 1, 'b', 'b', 2, 'c', 'c', 'd', 'e', 'f']

但我想要的是因为参数'abcdef'，当所有其他参数停止迭代时它不会停止迭代，对吧？我只想打印['d','e','f']

因此，所需的结构应该是：

def generator(*args):
    blah blah

a = generator('abc', 'abcdef', [1,2])
print([i for i in a])

>>>['d','e','f']

我的功能有什么问题吗？

Answer 1

如果你定义一些辅助函数，任务会更容易

vals = ['abc', 'abcdef', [1, 2]]


def next_or_none(iterator):
    """Return the next item in the iterator, or None if the iterator is done.
    """
    try:
        return next(iterator)
    except StopIteration:
        return None


def myzip(*args):
    """Yield one element from each arg, yield None for arg that are done.
    """
    args = [iter(a) for a in args]
    while True:
        res = [next_or_none(a) for a in args]
        if all(v is None for v in res):  # make sure we stop when all iterators are exhausted
            return
        yield res

有了这些定义，您需要做的就是遍历 myzip 生成器，直到它每次迭代只提供一个值。

def remainder(*args):
    for nextarg in myzip(*args):
        notnones = [v for v in nextarg if v is not None]
        if len(notnones) == 1:
            # wait for all but one iterator to be done before yielding.
            yield notnones[0]

print(list(remainder(*vals)))

Answer 2

试试这个：

在此代码中，仅对最大参数执行迭代，并且仅从其较大的位置开始。

def generator(*args):                                     
    sorts = sorted(args, key=len, reverse=True)           
    choose = sorts[0][len(sorts[0])-len(sorts[1]):]       
    gen = iter(choose)                                    
    while True:                                           
        yielded = False                                   
        try:                                              
            yield next(gen)                               
            yielded = True                                
        except StopIteration:                             
            pass                                          
        if not yielded:                                   
            return                                        
a = generator('abc', 'abcdef', [1,2])                     
print([i for i in a])