Python:协程 - 停止迭代异常

Question

我正在尝试使用 .send() 来输入字典。我的代码片段在下面

def coroutine(func):
    def start(*args, **kwargs):
        cr = func(*args, **kwargs)
        next(cr)
        return cr
    return start
@coroutine
def putd(di):
    print("via coroutines adding a key : value to dictionary")
    try:
        item = yield
        for key, value in item.items():
            if key in di:
                print("Key : {0} already exists".format(key))
            else:
                di[key] = value
        print(di)
    except StopIteration :
        print("yield frame got closed")

di = {}
gobj = putd(di)
gobj.send({"plan" : "shuttle"})
gobj.close()

我相信我正在正确处理exception，但我仍然StopIteration例外。

scratch.py
Traceback (most recent call last):
via coroutines adding a key : value to dictionary
{'plan': 'shuttle'}
File "scratch.py", line 39, in <module>
    gobj.send({"plan" : "shuttle"})
StopIteration
Process finished with exit code 1

是我没有正确处理该异常还是我错过了什么？非常感谢帮助。

Answer 1

您的协程在首次发送/屈服后退出。这将生成一个StopIteration，您无法在协程本身中处理它，而只能在调用 send 时处理。从文档中：

send（） 方法返回生成器生成的下一个值，或者 如果生成器退出而不产生另一个，则引发停止迭代 价值。

@coroutine
def putd(di):
    print("via coroutines adding a key : value to dictionary")
    try:
        item = yield
        for key, value in item.items():
            if key in di:
                print("Key : {0} already exists".format(key))
            else:
                di[key] = value
        print(di)
    except StopIteration :
        print("yield frame got closed")
    # here is an implicit  return None  which terminates the coroutine

我猜你想让协程保持活动状态，接受任意数量的发送，直到显式关闭：

@coroutine
def putd(di):
    print("via coroutines adding a key : value to dictionary")
    try:
        while True:
            item = yield
            for key, value in item.items():
                if key in di: 
                    print("Key : {0} already exists".format(key))
                else:
                    di[key] = value
            print(di)
    except GeneratorExit:
        print("yield frame got closed")

请注意，现在捕获了GeneratorExit异常。