ObjectivesThis exercise is designed to give you an introduction to sending and receiving ROS messages. If you run into any challenges, please reach out to the teaching team via Slack for help. Show
Additional ResourcesWe highly recommend that you check out the ROS resources page to learn more about ROS and tools that you may find useful while ROS programming. Let's Send and Receive Some ROS Messages!Create a new ROS package Let's navigate to our directory within our
Then be
sure to run the
Note: Every time you create a new package, change the package dependencies or anything in the Create a ROS node that publishes ROS messages We're going to write Python code to construct a ROS node that publishes the location of a point in space (with x, y, and z coordinates) twice per second. Create a new python file named
The first line (
You should see the following output:
We see that the In order to instantiate a
Next, we'll need to initialize our Python ROS node with a name, this is essential for your node to start communicating with ROS Master. Each ROS node must have a unique name. If you try to run two nodes with the same name, ROS will throw an error.
Now, we can define the components (header and point) of the
We set the header
If you were to print out
Note: It's also possible to define a
Now let's publish our
Now, let's run our code! Before running your code, you'll need to make sure that your script is executable:
In a first terminal run roscore. In a second terminal, we can run our code by executing the following:
To check that our ROS node is really sending our
You should see your Create a ROS node that subscribes to ROS messages using callback functions In addition to publishing ROS messages, it's equally important to understand how ROS nodes can "listen to" or subscribe to ROS messages that are published by other nodes. This is accomplished with ROS
callback functions. We'll now write a second Python script to construct a ROS node that subscribes to our Create a new Python script named
In these lines, we've ensured that this script will be
executed as a Python script (line 1), provided a descriptive comment of the ROS node (line 2), imported the necessary libraries (lines 3-4), and initialized our ROS node with the name Next, we'll set up our callback function. This function will be called every time a message is published to a specified ROS topic (in our case, the
Remember that Now, we'll set up our node to subscribe to the
As you can see above, when we set up our subscriber, we must give it the ROS topic to subscribe to (argument 1), the type of message published to that topic (argument 2), and the callback function name (argument 3). We'll need one final line that will keep our ROS node running until we're ready to shut it down:
That's it! Test it out, and you should
see that your Making your code object-orientedThe code we produced above is a great introduced to programming in ROS, however, as our programs become more complex we'll want to use object-oriented techniques to structure our code. Our next task is going to be editing the two ROS nodes we just wrote (
Here's an example: Sample SolutionsAt the following link, you can find sample solutions for all of the scripts written in this homework exercise. AcknowledgmentsThis coding exercise was based on the exercise presented in A Computational Introduction to Robotics course's Day 02 page. How do I run a Python program in ROS?Let's go!. Step 1: Create an account and Login to Robot Ignite Academy. On Robot Ignite Academy, you get access to the best online ROS courses and environment. ... . Step 2: Create a ROS package and some Python and C++ code. ... . Step 3: Master the Concept – Python vs C++ in ROS.. How do I run a Python script in ROS package?Related: For the Cpp version of this tutorial, check out how to import a Cpp header from another ROS package.. Setup a package with a Python module.. Write your Python module.. Install the Python module in your ROS environment. setup.py. CMakeLists.txt. package.xml. ... . Use your module in another ROS package.. Can I use Python in ROS?Just testing or learning ROS
If you're not a C++ expert, or if you're also new to programming, just go with Python for your learning journey. You will be able to discover all ROS core concepts with Python, and you'll remove the entry barrier of Cpp.
How do I run a node in ROS Python?Edit CMakeLists. txt to change the name of the executable(s) to build, and the source files that are used.. Set up only the parts you want to use from the examples.. Import your new custom messages and dynamic reconfigure configurations.. How do I run a Python script in RStudio?Run Python Scripts in the RStudio IDE
To get started writing Python in the RStudio IDE, go to File, New File, then Python Script. Code just as you would in an R script. The RStudio IDE provides several useful tools for your Python development: The RStudio environment pane displays the contents of Python modules.
Should I use C++ or Python for ROS?The main languages for writing ROS code are C++ and Python, C++ being preferred due to better performance.
|