我怎么知道发电机一开始是否空了？

Question

有没有一种简单的方法可以测试生成器是否没有任何东西，例如peek，hasNext，isEmpty等？

Answer 1

建议：

def peek(iterable):

    try:

        first = next(iterable)

    except StopIteration:

        return None

    return first, itertools.chain([first], iterable)

用法：

res = peek(mysequence)

if res is None:

    # sequence is empty.  Do stuff.

else:

    first, mysequence = res

    # Do something with first, maybe?

    # Then iterate over the sequence:

    for element in mysequence:

        # etc.