How to set PYTHONPATH when I obtain "Import ROOT error . No module found"

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See if you have “pyroot” among: root-config --features

In principle you should not set ROOT related environment variables manually. You should simply:
source /full/path/to/your/root/bin/

yes. i have pyroot. I actually figured it out just now . I had already done source command as you mentioned which didnt work. But when I set the correct path manually I got it.
Thanks anyway.

export PYTHONPATH=$(root-config --libdir)

Python does not add the current directory to sys.path, but rather the directory that the script is in. Add your project directory to either sys.path or $PYTHONPATH.

Also, set the PYTHONPATH to ‘.’ to solve this issue.

For a one-liner you could as easily do:

PYTHONPATH='.' your_python_script