How to prepend a string to all file names in a directory in a bash script?

for f in *.py; do mv "$f" "old-$f"; done

The above one-line will loop over all files in current directory with .py extension and prepend old- into the files.

So for example a file with name main.py will be renamed to old-main.py

#python #bash #script #prepend #move #rename #for