Since readline doc is sparse, Examples:

   https://stackoverflow.com/questions/5637124/tab-completion-in-pythons-raw-
input/5638688#5638688

also look at the rl package:

 https://rl.readthedocs.io/en/stable/overview.html

readline as provided in the standard library is missing some things. E.g. you can set
variables for use in the init file. rl claims to have extended api access to better
match the full GNU readline api.