title: Consume multiple queues in python / pika
body: <p>I am trying to create a consumer that would subscribe to multiple queues, and then process messages as they arrive. </p>
  
  <p>The problem is that when there is some data already present in the first queue, it consumes the first queue and never goes to consume the second queue.
  However, when the first queue is empty, it does go to the next queue, and then consumes both queues simultaneously.</p>
  
  <p>I had first implemented threading but want to steer clear of it, when pika library does it for  me without much complexity. Below is my code:</p>
  
  <pre><code>import pika
  
  mq_connection = pika.BlockingConnection(pika.ConnectionParameters('x.x.x.x'))
  mq_channel = mq_connection.channel()
  mq_channel.basic_qos(prefetch_count=1)
  
  
  def callback(ch, method, properties, body):
      print body
      mq_channel.basic_ack(delivery_tag=method.delivery_tag)
  
  mq_channel.basic_consume(callback, queue='queue1', consumer_tag="ctag1.0")
  mq_channel.basic_consume(callback, queue='queue2', consumer_tag="ctag2.0")
  mq_channel.start_consuming()
  </code></pre>