defining parameter to class in python

Question

Here is the code and the error that I am getting when I run the program . Can anyone explain what mistake I am doing? Also is it good to call a function of a class in the constructor like I did?

#!/usr/bin/env python

import rospy

class move_turtlebot(message):
    def __init__(self):
          self.pub=rospy.Publisher('/cmd_vel', Twist, queue_size=1)
          self.vel=Twist()
          rospy.loginfo("initiated!!")
         self.move(message)
    def move(self,message):
          if message=="STOP":
              rospy.loginfo("inside stop")
              self.vel=Twist()
              self.pub.publish(vel)
          elif message=="LEFT":
        #rest of code continues 
if __name__=="__main__":

   rospy.init_node('move_turtlebot')
   rospy.loginfo("here!")

   while not rospy.is_shutdown():
       ahead=move_turtlebot("FORWARD")

The error is:NameError: name 'message' is not defined at the line of defining class

In your __init__ method message has not yet been defined. Also elif is not indented correctly — Cory Kramer
– Cory Kramer, Commented Jan 11, 2020 at 17:01
Your class move_turtlebot inherits from message but this class is not defined/imported — Iain Shelvington
– Iain Shelvington, Commented Jan 11, 2020 at 17:02
I created an object of class "ahead=move_turtlebot("FORWARD"), the message variable is a string "FORWARD", isn't this sufficient. What does defining/importing class mean. — Hrushi
– Hrushi, Commented Jan 11, 2020 at 17:12

Christopher_Okoro · Accepted Answer · 2020-01-11 17:27:00Z

1

class move_turtlebot(message): # this means inheritance from a class message which u dont have or didnt define

For a class to have parameters they can be defined at the constructor like this (although there are variations) :

class move_turtlebot:
    def __init__(self,message):

edited Jan 11, 2020 at 17:27

answered Jan 11, 2020 at 17:18

Christopher_Okoro

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Comments

Oded BD · Accepted Answer · 2020-01-11 17:19:52Z

1

In your Class definition you are using message:

class move_turtlebot(message): <--- HERE

you don't have message defined, if you want to use message in your consructor add it to your __init__ function like so:

def __init__(self, message)

also I noted that the last line in your init function uses different indentation, if it is the same at your code, change it as well.

Hope it helps

answered Jan 11, 2020 at 17:19

Oded BD

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