loop_tracker

class loop_tracker:
    """
    Usage::
        >>> iterator = loop_tracker(n**2 for n in range(10))
        >>> sum(iterator)/len(iterator)
        28.5
    """
    def __init__(self, iterable):
        self.iterable = iterable
        self.size = 0
    def __iter__(self):
        return self
    def __next__(self):
        item = next(self.iterable)
        self.size += 1
        return item
    def __len__(self):
        return self.size