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Ask about the usage of the tilde '~'sign
what's the difference between :
pub = rospy.Publisher('~cmd_vel', Twist, queue_size=5)
and:
pub = rospy.Publisher('cmd_vel', Twist, queue_size=5)
By the way, what's the queue_size in the bracket mean?
Thank you!!
The tilde is due to namespacing. a ~ puts a topic or a parameter in the nodes private namespace (i.e. /some_ns/node_ns/private_topic), whereas without the tilde, it resides in the nodes namespace (i.e. /some_ns/topic). If you add a / instead of the tilde, you'll end up in the global namespace (/topic).
Python does not have the concept of a NodeHandle as C++, but in essence this is the same as ros::NodeHandle nh("~"), ros::NodeHandle nh("") and ros::NodeHandle nh("/").
About the queue_size, there is a good explanation on the wiki.
Asked: 2016-12-15 01:44:45 -0500
Seen: 4,305 times
Last updated: Dec 15 '16
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