Why does publisher declares queue a in Pika RabbitMQ?

I have gone through the fundamentals of RabbitMQ. One thing I figured out that a publisher does not directly publish on a queue. The exchange decides on which queue the message should be published based on routing-key and type of exchange (code below is using default exchange). I have also found an example code of publisher.

import pika, os, logging
logging.basicConfig()
# Parse CLODUAMQP_URL (fallback to localhost)
url = os.environ.get('CLOUDAMQP_URL', 'amqp://guest:guest@localhost/%2f')
params = pika.URLParameters(url)
params.socket_timeout = 5
connection = pika.BlockingConnection(params)
channel = connection.channel()
channel.queue_declare(queue='pdfprocess')
# send a message
channel.basic_publish(exchange='', routing_key='pdfprocess', body='User information')
print ("[x] Message sent to consumer")
connection.close()

In line #9 the queue is being declared. I am a bit confused because the publisher does not have to be aware of the queue. For example if it is using fanout exchange and there are 100 queues with different names, how the consumer know and declare 100 queues?

Answer

The consumer can declare the queue and bind it to the exchange when the consumer connects to RabbitMQ. A fanout exchange then copies and routes a received message to all queues bound to it, regardless of routing keys or pattern matching as with direct and topic exchanges.

So no, the publisher does not have to be aware of all queues bound to the exchange. However, the publisher can ensure that the queue exists to ensure that the code will run smoothly, but that is of more importance for other exchange types.