We have tried to almost entirely mimic todo.sh's behavior. It'll just be easier to list the differences.
If you would rather use python3 for your todo.py script, we support it! Just change the first line of the script from
Assuming of course that you have python3 installed along with python2. If you only have python3 installed, you should not have to do this.
It is usually easier to simply install the script to a local directory like $HOME/bin so you can always make this executable from any directory by adding that path to your PATH variable, e.g. export PATH="$PATH:$HOME/bin".