python - 我如何知道生成器是否从一开始就为空？

Question

是否有一种简单的方法来测试生成器是否没有项目，例如 peek、hasNext、isEmpty 等类似的东西？

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.