python generator with check for empty condition

Question

python generators are good replacements for lists in most cases expect where I would like to check for empty condition which is not possible with plain generators. I am trying t

Answer 1

I would not usually implement this kind of generator. There is an idiomatic way how to test if a iterator it is exhausted:

try:
    next_item = next(it)
except StopIteration:
    # exhausted, handle this case

Substituting this EAFP idiom by some project-specific LBYL idiom seems confusing and not beneficial at all.

That said, here is how I would implement this if I really wanted to:

class MyIterator(object):
    def __init__(self, iterable):
        self._iterable = iter(iterable)
        self._exhausted = False
        self._cache_next_item()
    def _cache_next_item(self):
        try:
            self._next_item = next(self._iterable)
        except StopIteration:
            self._exhausted = True
    def __iter__(self):
        return self
    def next(self):
        if self._exhausted:
            raise StopIteration
        next_item = self._next_item
        self._cache_next_item()
        return next_item
    def __nonzero__(self):
        return not self._exhausted