【说站】python coroutine的运行过程

"""
# BEGIN CORO_AVERAGER_TEST
    >>> coro_avg = averager()  # <1>
    >>> next(coro_avg)  # <2>
    >>> coro_avg.send(10)  # <3>
    10.0
    >>> coro_avg.send(30)
    20.0
    >>> coro_avg.send(5)
    15.0
# END CORO_AVERAGER_TEST
"""
def averager():
    total = 0.0
    count = 0
    average = None
    while True:  # <1>
        term = yield average  # <2>
        total += term
        count += 1
        average = total/count