Rabbitmq and Python NameError: global name problem

Question

I'm trying to send a JSON to Rabbitmq. this is my producer and it works properly:

import pika
import json

credentials = pika.PlainCredentials('admin', '123')
parameters = pika.ConnectionParameters('192.168.1.11',
                                       5672,
                                       '/',
                                       credentials)
connection = pika.BlockingConnection(parameters)
channel = connection.channel()
channel.queue_declare(queue='myapp')

message = {'fname': 'test', 'lname': 'test'}

channel.basic_publish(exchange='',
                      routing_key='myapp',
                      body=json.dumps(message),
                      properties=pika.BasicProperties(
                         delivery_mode = 2,

                      ))
print(" [x] Sent %r" % message)

connection.close()

This is the receiver and it's not ok:

import pika
import time
import json

credentials = pika.PlainCredentials('admin', '123')
parameters = pika.ConnectionParameters('192.168.1.12',
                                       5672,
                                       '/',
                                       credentials)
connection = pika.BlockingConnection(parameters)
channel = connection.channel()
channel.queue_declare(queue='myapp')

def callback(ch, method, properties, body):
    myjson = json.loads(body)
    global fname
    global lname
    fname = myjson["fname"]
    lname = myjson["lname"]
    my_func(fname,lname)

channel.basic_qos(prefetch_count=1)
channel.basic_consume(queue='myapp',
                      auto_ack=True,
                      on_message_callback=callback)
channel.start_consuming()
def my_func(fname,lname):
    pass

when I run scripts the receiver show below problem :

NameError: global name 'my_func' is not defined

Answer 1

The issue is due to this function in your receiver.py

channel.start_consuming()

The function will block the program there and prevent it from seeing my_func(). On the other hand, the code analysis tool, e.g. pylint, may mostly likely fail to detect such error.

An easy solution is to change the code to

def callback(ch, method, properties, body):
    myjson = json.loads(body)
    global fname
    global lname
    fname = myjson["fname"]
    lname = myjson["lname"]
    my_func(fname,lname)

def my_func(fname,lname):
    pass

channel.basic_qos(prefetch_count=1)
channel.basic_consume(queue='myapp',
                      auto_ack=True,
                      on_message_callback=callback)
channel.start_consuming()

A more complex solution is to create your own class or method and run start_consuming() in a asynchromized way. Here is my example:

def listen(self, exchange, routing, callback):
    self.ReceiveChannel = self.connection.channel()
    consumer_thread = threading.Thread(target=self.__consumer__, args=[exchange, routing, callback])
    consumer_thread.start()