python - Python：协程 - StopIteration 异常

Question

我正在尝试使用.send(). 我的代码片段如下

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()

而且我相信我处理exception得当，但我仍然遇到StopIteration异常。

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

我没有正确处理该异常还是我遗漏了什么？非常感谢任何帮助。

标签： pythonpython-3.xgeneratorcoroutinestopiteration

Answer 1

您的协程在第一次发送/屈服后退出。这会生成 aStopIteration并且您无法在协程本身中处理它，但只能在调用send. 从文档：

send() 方法返回生成器产生的下一个值，或者如果生成器退出而没有产生另一个值，则引发 StopIteration。

@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

我想你想让协程保持活动状态，接受尽可能多的发送，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GeneratorExit异常已被捕获。