I am trying to write a code that allows the drone to first takeoff then increase its altitude before moving forward for a certian distance before landing again. The problem is that the drone takeoff and hovers and then lands without executing anyother commands written to it in the middle. I am running the test code in gazebo. What would be the best solution for this?

#!/usr/bin/env python 

#import library ros 
import rospy 
from geometry_msgs.msg import Twist
from std_msgs.msg import Empty
from std_msgs.msg import String
from ardrone_autonomy.msg import Navdata


class AutoFlight():

    def __init__(self):
        self.status = ""
        self.pub_takeoff = rospy.Publisher('/ardrone/takeoff',Empty,queue_size =10) #Drone Takeoff
        self.land_drone = rospy.Publisher('ardrone/land',Empty,queue_size=10) #land drone
        self.command = rospy.Publisher('/cmd_vel',Twist,queue_size = 10) 
        self.Reset = rospy.Publisher('/ardrone/reset',Empty,queue_size =10)
        self.rate=rospy.Rate(10)
        self.sleep_mode= rospy.sleep(10)
        #self.Shutdown_mode = rospy.on_shutdown(self.land_drone)



    def Take_off(self):
        self.pub_takeoff.publish(Empty())
        self.sleep_mode

    def Land (self):
        self.land_drone.publish(Empty())
        self.sleep_mode

    def Reset_drone(self):
        self.Reset(Empty())


    def Command_directions(self, lin_x=0,lin_y=0,lin_z=0,ang_x=0,ang_y=0,ang_z=0):
        self.Control = Twist()

        self.Control.linear.x = lin_x 
        self.Control.linear.y = lin_y
        self.Control.linear.z = lin_z
        self.Control.angular.x = ang_x
        self.Control.angular.y = ang_y
        self.Control.angular.z = ang_z
        self.rate.sleep()



if __name__== "__main__":

    rospy.init_node('my_drone_node',anonymous=True) #Node Initiaton
    drone = AutoFlight()

    forward_dist = 0 #Initialization of forward movement acceleration
    altitude = 0 # Iniatialization of the altitude -
    try:
       drone.Take_off()
       rospy.sleep(1)
       drone.Command_directions(0,0,0,0,0,0)

       while not rospy.is_shutdown():

            if altitude < 40: 
                drone.Command_directions(0,0,1,0,0,0)
                #altitude =+ 1
        altitude = altitude + 1
                rospy.sleep(1)
                #print("altitude:" ,altitude)
                drone.Command_directions(1,0,0,0,0,0)

            elif altitude < 50:
                drone.Command_directions(0,0,0,0,0,0)
                print("we are hovering")
          #  if forward_dist < 15:
               #     drone.Command_directions (1,0,0,0,0,0)
                #    forward_dist +=1
            altitude = altitude + 1

            #drone.Land()           

    except rospy.ROSInterruptException:
             pass