Question

我的问题：

我想知道Python中是否存在从“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？

我的方案：

我有(producer) > (filter) > (consumer)协程管道来处理基于文本的表并从中构建字典列表。我希望将consumer中构建的对象返回给producer的原始调用者。

我的方法：

我的方法是设置每个协程检查的唯一完成处理信号。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。 consumer只会产生当前值。

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。
基于类的方法，包含常规子例程。

为什么我应该重新考虑这些因为我的情景也是受欢迎的。

我的实施：

以下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

Answer 1

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恰好是向生成器发送事件或状态变化的信号。此外，when an exception is thrown to a generator，

[i] f 生成器捕获异常并产生另一个值，即 g.throw（）的返回值。

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

是否有一种从协程端点返回值的标准方法

1 个答案: