How to run ROS command from a python script?

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Hello! I need some help as I was trying to write a python script which could run some ROS commands, such as $rostopic list and $rostopic echo(while some nodes are running). I tried something like the following, but none of them works. when I tried this:

os.system("rostopic list")

I got this error when I ran the above: sh: 1: rostopic: not found

Or this:

subprocess.call(["rostopic", "list"])

It was not working and a error message was given like this "FileNotFoundError: [Errno 2] No such file or directory: 'rostopic'"

I was thinking about execute a shell script from my python script, but I don't know how to write one for running ROS commands.

I appreciate any help!