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Variable namespaces in classes (Python3)

asked 2022-04-11 08:16:06 -0500

WarTurtle gravatar image

I am having difficulties using variable namespaces with python3 classes

Here's a snippet of code that I would think would work, but doesn't.

In the BasicNavigator class:

    self.namespace = ''

    self.localization_pose_sub = self.create_subscription(PoseWithCovarianceStamped,
                                                          self.namespace + '/amcl_pose',
                                                          self._amclPoseCallback,
                                                          amcl_pose_qos)

In main:

navigator = BasicNavigator()

navigator.namespace = "robot1"

This does not work, it does not recognize the "robot1" in the class.

Instead, if I remove the self.namespace and just write the topic name as such: 'robot1/amcl_pose' it works, but I need to be able to have a variable amount of robots...

What am I doing wrong?

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Comments

Very likely the subscription is getting created beforeself.namespace is being set to robot1. What if you made the constructor of BasicNavigator take in a namespace, so that you can do something like self.namespace = namespace?

abhishek47 gravatar image abhishek47  ( 2022-04-11 11:31:38 -0500 )edit

As the previous comment said, you need to rearrange when you're setting the namespace and when the subscription is created.

aprotyas gravatar image aprotyas  ( 2022-04-11 14:50:09 -0500 )edit

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answered 2022-04-12 07:37:06 -0500

WarTurtle gravatar image

Thanks, abhishek47 and aprotyas for your comments. It worked by creating a method with the namespace argument.

In BasicNavigor class:

def createSubscriptions(self, namespace):
    self.localization_pose_sub = self.create_subscription(PoseWithCovarianceStamped,
                                                          namespace + 'amcl_pose',
                                                          self._amclPoseCallback,
                                                          amcl_pose_qos)

And then I call this in main:

navigator = BasicNavigator()

namespace = "robot1"
navigator.createSubscriptions(namespace)

Not sure if this is exactly what you wanted me to try, but it works, so I'm happy :)

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Something along these lines, yes. Good to know that it worked!

aprotyas gravatar image aprotyas  ( 2022-04-13 00:18:37 -0500 )edit

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Asked: 2022-04-11 08:16:06 -0500

Seen: 45 times

Last updated: Apr 12