A node that's a subscriber, a publisher and uses dynamic parameters [Python]

edit

Suppose I have defined two custom dynamic parameters, gain1 and gain2, in a cfg file. I would like to use these in a node that subscribes and publishes to two topics. Here's what i tried:

import rospy
from std_msgs.msg import Float64
from dynamic_reconfigure.server import Server
from myPack.cfg import paramConfig

def param_callback(config, level):
      gain1 = config.gain1
      gain2 = config.gain2
      return config

def callback1(msg):
      in1 = msg.data

def callback2(msg):
      in2 = msg.data

rospy.init_node('mixer')
srv = Server(paramConfig, param_callback)

sub1 = rospy.Subscriber('in1', Float64, callback1)
sub2 = rospy.Subscriber('in2', Float64, callback2)

pub1 = rospy.Publisher('out1', Float64)
pub2 = rospy.Publisher('out2', Float64)

out1 = Float64()
out2 = Float64()

while not rospy.is_shutdown():
      out1.data = in1*gain1
      out2.data = in2*gain2

      pub1.publish(out1)
      pub2.publish(out2)

But it seems the subscribers callbacks don't work. This error is given for the first line of the while loop.

 NameError: name 'in1' is not defined

Note that the subscription and parameter server code work fine individually.

Am I using the right method?

Update: As suggested by gvdhoorn, I had to define gain1 and gain2 as global variables and initialize in1 and in2 before the while loop. The latter because the program could reach the while loop before a callback. In this case, in1 is still undefined and I would receive the same error .

I feel this method is a bit inelegant and as gvdhoorn pointed out, using a class instead of global variables is better programming.