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，我认为是由于我的 A) 对 Python 和一般编码很陌生，B) 我不理解如何在函数之间传递变量，当它们在单独的线程中运行并且已经在中传递参数时接收函数名称末尾的括号。
我之所以这么想，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称并在括号中提供要传递的变量来在函数之间传递变量，在括号中，一个基本示例如下所示：
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
我需要使用线程的代码的工作版本如下所示 - 它使用直接函数（无线程）并且我正在使用 pika 通过 pika 回调函数从（RabbitMQ）队列接收消息，然后我通过在“处理功能”的“回调”功能中收到的消息正文：
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...
这很好用，但是我想将其转换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”如下所示：
def processing_function(channel, body):
我收到一条错误消息：
[function_name] is missing 1 positional argument: 'body'
我知道在使用线程时需要更多代码，我在下面包含了我用于线程的实际代码，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
这在运行时产生错误
process_body() missing 1 required positional argument: (body)
我不明白这是为什么或如何解决它。
在进一步研究并使用代码时，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))
这样写：
t2 = threading.Thread(target=process_body)
然后代码似乎可以按需工作 - 我还在 htop 中看到多个脚本进程，因此看起来线程正在工作 - 我已经离开脚本处理 24 小时 + 并且没有收到任何错误...