Why did the pub before rospy.spin() not work?

melodic

asked 2021-03-31 02:24:17 -0500

Win
1 ●1 ●2 ●2

updated 2021-04-01 22:04:54 -0500

jayess
6155 ●26 ●85 ●92

I want to use Python to publish a topic before the spin. There is no problem with data printing, but there is no data in the echo outside, It can work in the callbacks.

self.pub_distance = rospy.Publisher('/path_distance',Int32,queue_size=10)
def run(self):
        distance_ = Int32()
        distance_.data = self.generate_path(0, self.path.keys()[-1])
        print distance_ #Here's a value printed on the screen
        self.pub_distance.publish(distance_) #But this doesn't work!!!
        rospy.spin()

edit retag flag offensive close merge delete

Comments

Too little info! Could you include your code?

abhishek47 ( 2021-03-31 11:19:04 -0500 )edit

already added.

Win ( 2021-04-01 23:07:29 -0500 )edit

rospy.spin() is blocking and sets off the "event loop" (an "infinite while" if you will). How/where do you call run()?

abhishek47 ( 2021-04-02 00:54:02 -0500 )edit

this code is my simple version，run() is running in main function.

Win ( 2021-04-02 01:42:13 -0500 )edit

I can understand spin(), but why did the pub is not working?

Win ( 2021-04-02 01:46:49 -0500 )edit

Did you solve this problem because i am facing with the same problem right now?

Anonymous ( 2022-11-22 02:35:34 -0500 )edit

1

Two solutions, delay 1s before pub or make publish global (move out of class)

Win ( 2022-12-02 00:05:47 -0500 )edit

add a comment

-2

answered 2021-04-19 09:12:38 -0500

Win
1 ●1 ●2 ●2

updated 2022-12-02 04:54:14 -0500

两种解决方法，在pub前延迟1s或者将publish定义为全局（移出class）

Two solutions, delay 1s before pub or make publish global (move out of class)

edit flag offensive delete link

Comments

I'm glad you solved it. If you like, you can leave it in English. I think it will help others who follow.

By the way, is the code of the solution like this?

1

self.pub_distance = rospy.Publisher('/path_distance',Int32,queue_size=10)
def run(self):
        distance_ = Int32()
        distance_.data = self.generate_path(0, self.path.keys()[-1])
        print distance_ #Here's a value printed on the screen
        rospy.sleep(1.0) # added
        self.pub_distance.publish(distance_)
        rospy.spin()

2

pub_distance = rospy.Publisher('/path_distance',Int32,queue_size=10) # changed
def run(self):
        distance_ = Int32()
        distance_.data = self.generate_path(0, self.path.keys()[-1])
        print distance_ #Here's a value printed on the screen
        pub_distance.publish(distance_) # changed
        rospy.spin()

miura ( 2021-04-19 09:31:58 -0500 )edit

Yes, it is right.

Win ( 2022-12-02 04:54:52 -0500 )edit

add a comment

0

answered 2021-04-02 08:04:06 -0500

miura

1908 ●1 ●171 ●24 https://twitter.com/miura

Probably, if you are not running spin(), the node is terminated before the topic is sent.

The topic will not be sent when you publish it. As a way to wait for it to be sent, spin() is an option.

It is important to note that callbacks are not always necessary here.

The topic will probably still be sent below.

self.pub_distance = rospy.Publisher('/path_distance',Int32,queue_size=10)
def run(self):
        distance_ = Int32()
        distance_.data = self.generate_path(0, self.path.keys()[-1])
        print distance_ #Here's a value printed on the screen
        self.pub_distance.publish(distance_) #But this doesn't work!
        # rospy.spin()
        Rate = rospy.Rate(10)
        while not rospy.is_shutdown():
                rate.sleep()

edit flag offensive delete link

Comments

I tried, this is invalid.

Win ( 2021-04-06 03:08:32 -0500 )edit

Thank you for trying it. There is no other cause I can think of. I'm looking forward to other people's answers.

miura ( 2021-04-06 08:19:55 -0500 )edit

add a comment

Why did the pub before rospy.spin() not work?

Comments

2 Answers

Comments

1

2

Comments

Question Tools

Stats

Related questions

Why did the pub before rospy.spin() not work? edit

Comments

2 Answers

Comments

1

2

Comments

Question Tools

Stats

Related questions

Why did the pub before rospy.spin() not work?