Question

我正在尝试开发一个使用pika和线程模块的Python 3.6脚本。

我有一个问题，我认为这是由我的A）对Python和编码一般都很新，以及B）我不理解如何在函数之间传递变量，当它们在不同的线程中运行并且已经被传递了接收函数名称末尾括号中的参数。

我认为这是因为当我不使用线程时，我可以简单地通过调用接收函数名来传递函数之间的变量，并提供要传递的变量，在括号中，一个基本的例子如下所示：

def send_variable():
    body = "this is a text string"
    receive_variable(body)

def receive_variable(body):
    print(body)

运行时，打印：

this is a text string

下面显示了我需要使用线程的代码的工作版本 - 这使用直接函数（没有线程），我使用pika通过pika回调函数从（RabbitMQ）队列接收消息，I然后将“回调”函数中收到的消息正文传递给“处理函数”：

import pika
...mq connection variables set here...


# defines username and password credentials as variables set at the top of this script
    credentials = pika.PlainCredentials(mq_user_name, mq_pass_word)

# defines mq server host, port and user credentials and creates a connection
    connection = pika.BlockingConnection(pika.ConnectionParameters(host=mq_host, port=mq_port, credentials=credentials))

# creates a channel connection instance using the above settings
    channel = connection.channel()

# defines the queue name to be used with the above channel connection instance
    channel.queue_declare(queue=mq_queue)


def callback(ch, method, properties, body):

# passes (body) to processing function
    body_processing(body)

# sets channel consume type, also sets queue name/message acknowledge settings based on variables set at top of script
    channel.basic_consume(callback, queue=mq_queue, no_ack=mq_no_ack)
# tells the callback function to start consuming
    channel.start_consuming()
# calls the callback function to start receiving messages from mq server
    callback()
# above deals with pika connection and the main callback function


def body_processing(body):
    ...code to send a pika message every time a 'body' message is received...

这很好但我想将其翻译为在使用线程的脚本中运行。当我这样做时，我必须将参数'channel'提供给在其自己的线程中运行的函数名称 - 然后我尝试包含'body'参数，以便'processing_function'看起来如下所示：

def processing_function(channel, body):

我收到错误说：

[function_name] is missing 1 positional argument: 'body'

我知道在使用线程时需要更多代码，我已经包含了下面用于线程化的实际代码，以便您可以看到我在做什么：

...imports and mq variables and pika connection details are set here...

def get_heartbeats(channel):
channel.queue_declare(queue=queue1)
#print (' [*] Waiting for messages. To exit press CTRL+C')

    def callback(ch, method, properties, body):

        process_body(body)

        #print (" Received %s" % (body))

    channel.basic_consume(callback, queue=queue1, no_ack=no_ack)
    channel.start_consuming()


def process_body(channel, body):
    channel.queue_declare(queue=queue2)
    #print (' [*] Waiting for Tick messages. To exit press CTRL+C')

# sets the mq host which pika client will use to send a message to
    connection = pika.BlockingConnection(pika.ConnectionParameters(host=mq_host))
# create a channel connection instance
    channel = connection.channel()
# declare a queue to be used by the channel connection instance
    channel.queue_declare(queue=order_send_queue)
# send a message via the above channel connection settings
    channel.basic_publish(exchange='', routing_key=send_queue, body='Test Message')
# send a message via the above channel settings
# close the channel connection instance
    connection.close()


def manager():

# Channel 1 Connection Details - =======================================================================================

    credentials = pika.PlainCredentials(mq_user_name, mq_password)
    connection1 = pika.BlockingConnection(pika.ConnectionParameters(host=mq_host, credentials=credentials))
    channel1 = connection1.channel()

# Channel 1 thread =====================================================================================================
    t1 = threading.Thread(target=get_heartbeats, args=(channel1,))
    t1.daemon = True
    threads.append(t1)
    # as this is thread 1 call to start threading is made at start threading section

# Channel 2 Connection Details - =======================================================================================

    credentials = pika.PlainCredentials(mq_user_name, mq_password)
    connection2 = pika.BlockingConnection(pika.ConnectionParameters(host=mq_host, credentials=credentials))
    channel2 = connection2.channel()

# Channel 2 thread ====================================================================================================
    t2 = threading.Thread(target=process_body, args=(channel2, body))
    t2.daemon = True
    threads.append(t2)
    t2.start()  # as this is thread 2 - we need to start the thread here

# Start threading
t1.start()  # start the first thread - other threads will self start as they call t1.start() in their code block
for t in threads: # for all the threads defined
    t.join()  # join defined threads

manager()  # run the manager module which starts threads that call each module

运行时会产生错误

process_body() missing 1 required positional argument: (body)

我不明白为什么会这样或如何解决它。

感谢您抽出宝贵时间阅读此问题，我们非常感谢您提供的任何帮助或建议。

请记住，我是python和编码的新手，所以可能需要拼写出来的东西，而不是能够理解更多神秘的回复。

谢谢！

Answer 1

在进一步查看并使用代码时，似乎如果我编辑这些行：

def process_body(channel, body):

阅读

def process_body(body):

和

t2 = threading.Thread(target=process_body, args=(channel2, body))

所以它写着：

t2 = threading.Thread(target=process_body)

然后代码似乎按需工作 - 我也在htop中看到多个脚本进程，因此看起来线程正在工作 - 我已经让脚本处理24小时+并且没有收到任何错误......

Python - 在不同线程

1 个答案: