How to use data of subscriber to publish and command the robot?

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My main aim is to turn the robot to a specific angle. So, what I am trying to do is I have defined a subscriber and publisher in single node and then I will subscribe to the odometry data of the gazebo model through which I will calculate the yaw of the robot and until the robot gain the specific yaw I will command it a specific angular velocity. But the problem is when I define yaw in odometryCb it is not local variable so I can't use it in publisher part so tried defining variables in publisher it self but it is showing that sub has no attribute subscriber. Can anyone help me to find out how to deal it with?

#!/usr/bin/env python
import rospy
import roslib; roslib.load_manifest('firstrobot')
from std_msgs.msg import String
from nav_msgs.msg import Odometry
from std_msgs.msg import Header
from geometry_msgs.msg import Twist
import time
import math

TEXTFILE = open("data_pub.csv", "w")
TEXTFILE.truncate()

def odometryCb(msg):
   import csv
   #csvData=[['pose_x','pose_y','twist_x','twist_z', 'Orientation' ,'time']]
   x = msg.pose.pose.position.x
   y = msg.pose.pose.position.y
   v_x = msg.twist.twist.linear.x
   w = msg.twist.twist.angular.z
   q0 = msg.pose.pose.orientation.w
   q1 = msg.pose.pose.orientation.x
   q2 = msg.pose.pose.orientation.y
   q3 = msg.pose.pose.orientation.z
   yaw = math.degrees(math.atan2( 2.0*(q0*q3 + q1*q2),(1.0-2.0*(q2*q2 + q3*q3))))
   t= 1.0*msg.header.stamp.secs + 1.0*(msg.header.stamp.nsecs)/1000000000
   row = [ v_x, w, yaw, t]
   with open('data.csv', 'a') as csvFile:
      writer = csv.writer(csvFile)
      writer.writerow(row)
   csvFile.close()

def publisher():

pub = rospy.Publisher('robot_diff_drive_controller/cmd_vel', Twist, queue_size=10)
sub = rospy.Subscriber("robot_diff_drive_controller/odom", Odometry, odometryCb)
rospy.init_node('publisher', anonymous=True)
rate = rospy.Rate(10) # 10hz
cmd_vel = Twist()
odom = Odometry()
cmd_vel.linear.x=0.0
cmd_vel.angular.z=0.3
now = time.time()
du =  time.time()

x = sub.subscribe(odom.pose.pose.position.x)
y = sub.subscribe(odom.pose.pose.position.y)
v_x = sub.subscribe(odom.twist.twist.linear.x)
w = sub.subscribe(odom.twist.twist.angular.z)
q0 = sub.subscribe(odom.pose.pose.orientation.w)
q1 = sub.subscribe(odom.pose.pose.orientation.x)
q2 = sub.subscribe(odom.pose.pose.orientation.y)
q3 = sub.subscribe(odom.pose.pose.orientation.z)
yaw = math.degrees(math.atan2( 2.0*(q0*q3 + q1*q2),(1.0-2.0*(q2*q2 + q3*q3))))

while(yaw < 90):
    pub.publish(cmd_vel)
    rate.sleep()
# In ROS, nodes are uniquely named. If two nodes with the same
# node are launched, the previous one is kicked off. The
# anonymous=True flag means that rospy will choose a unique
# name for our 'listener' node so that multiple listeners can
# run simultaneously.

# spin() simply keeps python from exiting until this node is stopped
if __name__ == '__main__':
  publisher()