I started using it on one of my programs a while back. Ever since, whenever I type the tab key on a console (cmd.exe instance) with python running, I get a readline internal
pyreadline can be uninstalled by typing pip uninstall pyreadline in the command prompt. I was experiencing the same issue, but after uninstalling pyreadline, Tab key is working for me.
NOTE: To see the installed packages, type pip list in command prompt.