python学习05协程_2

1、停止协程与异常处理
2、协程返回值
协程中未处理的值会向上冒泡，传给next函数或send方法的调用方（即触发协程的对象）

def make_avg():
    total = 0
    count = 0
    avg = None
    while True:
        term = yield avg
        total += term
        count += 1
        avg = total / count

avg_coro = make_avg()

next(avg_coro)
print(avg_coro.send(5))
avg_coro.send('abc')#发送的不是数字，导致协程内部异常
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由于在协程内没有处理异常，协程会终止p y。如果尝试重新激活协程，会抛出StopIteration异常,所以终止协程可以通过发送某个哨符值，让协程退出。

class DemoException(Exception):
    pass

def demo_exc_handing():
    print('coroutine started')
    while True:
        try:
            x = yield

        except DemoException:
            print('DemoExcep')
        else:
            print('coroutine received: ',x)

    raise RuntimeError('this line shoule never run')

exc_coro = demo_exc_handing()
next(exc_coro)
exc_coro.send(2)
exc_coro.close()
from inspect import getgeneratorstate
print(getgeneratorstate(exc_coro))#查看状态
exc_coro2 = demo_exc_handing()
next(exc_coro2)
exc_coro2.send(1)
exc_coro2.throw(DemoException)#传入协程可以处理的异常
exc_coro2.throw(ZeroDivisionError)
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#协程返回值

from collections import namedtuple
Result = namedtuple('Result','count average')
def make_avg():
    total = 0
    count = 0
    avg = None
    while True:
        term = yield
        #为了返回值，协程必须正常终止
        if term is None:
            break
        total += term
        count += 1
        avg = total / count
    return Result(count,avg)
avg_coro = make_avg()
next(avg_coro)
print(avg_coro.send(10))
print(avg_coro.send(20))
try:
    avg_coro.send(None)
except StopIteration as e:
    result = e.vaule
print(result)
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