from time import time

class generators(object):
    """ My collection of useful generator examples in python
        by: Cody Kochmann """

    def started(generator_function):
        """ starts a generator when created """
        def wrapper(*args, **kwargs):
            g = generator_function(*args, **kwargs)
            next(g)
            return g
        return wrapper

    @staticmethod
    @started
    def sum():
        "generator that holds a sum"
        total = 0
        while 1:
            total += yield total

    @staticmethod
    @started
    def counter():
        "generator that holds a sum"
        c = 0
        while 1:
            yield c
            c += 1

    @staticmethod
    @started
    def avg():
        """ generator that holds a rolling average """
        count = 0.0
        total = generators.sum()
        i=0
        while 1:
            i = yield (total.send(i)*1.0/count if count else 0)
            count += 1

    @staticmethod
    @started
    def timer():
        """ generator that tracks time """
        start_time = time()
        previous = start_time
        while 1:
            yield time()-start_time