我的问题：

我想知道Python中是否存在用于从协程端点(又称“接收器”或“消费者”)返回值的“最佳实践”模式.更一般地说,您将如何处理以下情况？

我的情景：

我有我的(制片人)> (过滤器)> (使用者)coroutine管道来处理基于文本的表并从中构建字典列表.我希望将在consumer中构建的对象返回给producer的原始调用者.

我的方法：

我的方法是设置一个独特的完成处理信号,每个协程都会检查.如果它听到信号,那么它将信号传递给它的孩子并产生返回的值.消费者只是产生其当前价值.

替代方法：

我考虑过：

>使用全局来保持所需对象“返回”给调用者.
>具有常规子例程的基于类的方法.

我应该为我的方案重新考虑这些的原因也是受欢迎的.

我的实施：

这是我所做的简化版本,包括所有关键组件.

import uuid

FINISH_PROCESSING_SIGNAL = uuid.uuid4()

def coroutine(func):
    def start(*args,**kwargs):
        cr = func(*args,**kwargs)
        cr.next()
        return cr
    return start


# Sink
@coroutine
def list_builder():
    # accepts objects and adds them to a list
    _list = []
    try:
        while True:
            data = (yield)
            if data is FINISH_PROCESSING_SIGNAL:
                yield _list
                break
            _list.append(data)
    except GeneratorExit:
        pass

# Filter
@coroutine
def user_data_filter(target=None):

    if target is None:
        target = list_builder()

    header = "-+-"
    footer = "Transfer Packets"
    username = "User Name"
    fullname = "Full Name"
    note = "Description"

    try:
        while True:
            user = {}
            data = (yield)
            if data is FINISH_PROCESSING_SIGNAL:
                yield target.send(FINISH_PROCESSING_SIGNAL)
                break
            line = data
            if header in line:
                while True:
                    line = (yield)
                    if footer in line:
                        target.send(user)
                        break
                    elif username in line:
                        user["username"] = line.split('|')[1]
                    elif fullname in line:
                        user["fullname"] = line.split('|')[1]
                    elif note in line:
                        user["note"] = line.split('|')[1]

    except GeneratorExit:
        target.close()

# Producer
def process_users_table(table, target=None):

    if target is None:
        target = user_data_filter()

    lines = table.split('\r\n')
    for line in lines:
        target.send(line)
    processed_data = target.send(FINISH_PROCESSING_SIGNAL)
    return processed_data



if __name__ == '__main__':

    test_users_table = \
    """
    Item            |Value\r\n
    ----------------+-----------------------\r\n
    User Name       |alice\r\n
    Full Name       |Alice Doe\r\n
    Description     |\r\n
    Transfer Packets|0\r\n
    ----------------+-----------------------\r\n
    User Name       |bob\r\n
    Full Name       |Bob Tables\r\n
    Description     |\r\n
    Transfer Packets|0\r\n
    """

    users = process_users_table(test_users_table)
    print users

最佳答案 您发信号通知消费者终止的方法很好,并且与使用多处理或线程化队列时的操作相符.但是,生成器还有一种方法可以抛出异常(而不是发送值),而
the purpose of throw恰好是向生成器发出事件或状态变化的信号.而且,
when an exception is thrown to a generator,

[i]f the
generator catches the exception and yields another value, that is
the return value of g.throw().

这似乎非常适合您的用例.您可以抛出FINISH_PROCESSING_SIGNAL异常,而不是发送FINISH_PROCESSING_SIGNAL值,并使用try..except来产生最终值.

class FINISH_PROCESSING_SIGNAL(Exception): pass

def coroutine(func):
    def start(*args,**kwargs):
        cr = func(*args,**kwargs)
        cr.next()
        return cr
    return start


# Sink
@coroutine
def list_builder():
    # accepts objects and adds them to a list
    _list = []
    try:
        while True:
            data = (yield)
            _list.append(data)
    except FINISH_PROCESSING_SIGNAL:
        yield _list

# Filter
@coroutine
def user_data_filter(target=list_builder()):
    header = "-+-"
    footer = "Transfer Packets"
    username = "User Name"
    fullname = "Full Name"
    note = "Description"
    try:
        while True:
            user = {}
            data = (yield)
            line = data
            if header in line:
                while True:
                    line = (yield)
                    if footer in line:
                        target.send(user)
                        break
                    elif username in line:
                        user["username"] = line.split('|')[1]
                    elif fullname in line:
                        user["fullname"] = line.split('|')[1]
                    elif note in line:
                        user["note"] = line.split('|')[1]
    except FINISH_PROCESSING_SIGNAL as err:
        # Pass along the Exception to the target, and yield its result back
        # to the caller
        yield target.throw(err)

# Producer
def process_users_table(table, target=user_data_filter()):
    lines = table.split('\r\n')
    for line in lines:
        target.send(line)
    processed_data = target.throw(FINISH_PROCESSING_SIGNAL)
    # processed_data = target.close()
    return processed_data



if __name__ == '__main__':

    test_users_table = \
    """
    Item            |Value\r\n
    ----------------+-----------------------\r\n
    User Name       |alice\r\n
    Full Name       |Alice Doe\r\n
    Description     |\r\n
    Transfer Packets|0\r\n
    ----------------+-----------------------\r\n
    User Name       |bob\r\n
    Full Name       |Bob Tables\r\n
    Description     |\r\n
    Transfer Packets|0\r\n
    """

    users = process_users_table(test_users_table)
    print users