# Exercise3.4 in service

**URL:** <https://get-help.theconstruct.ai/t/exercise3-4-in-service/739>\
**Category:** ROS Basics In 5 Days (C++)\
**Created:** [September 16, 2019, 6:13am UTC](https://get-help.theconstruct.ai/t/exercise3-4-in-service/739 "2019-09-16T06:13:13Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![bayodesegun](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/bayodesegun/32/10684_2.png) [@bayodesegun](https://get-help.theconstruct.ai/u/bayodesegun)\
**Post date:** [September 16, 2019, 8:44am UTC](https://get-help.theconstruct.ai/t/exercise3-4-in-service/739/2 "2019-09-16T08:44:47Z")

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Hi @tjdtkadn, welcome to the community!

I think the post below will answer your question, if you are taking the Python course.

> **[ERROR: cannot launch node of type \[package/file.py\]: can't locate node...](https://get-help.theconstruct.ai/t/error-cannot-launch-node-of-type-package-file-py-cant-locate-node-file-py-in-package-package/54)**
>
> This error is very common when using ROS to launch a python node, either via rosrun or roslaunch. SOLUTION: Does the file file.py… exist in the package package? If not, create it! (Does the package itself exist and is it spelled correctly?)....

However, if you are on the C++ course (as it seems now), then please check that you have…

- Edited `CMakeLists.txt` and `package.xml` as instructed.
- Compiled using `catkin_make`.
- Run `source devel/setup.bash` on every terminal window, after catkin\_making..

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_[View the full topic](https://get-help.theconstruct.ai/t/exercise3-4-in-service/739)._