Simple extensible rock paper scissors.

rps.py

from random import choice

logic = {
  "rock": ["scissors"],
  "paper": ["rock"],
  "scissors": ["paper"]
}
choices = list(logic.keys())

def round(human, computer):
  try:
    if computer in logic[human]:
      print(f"you win! {human} beats {computer}.")
    elif human in logic[computer]:
      print(f"computer wins: {computer} beats {human}.")
    else:
      print("tie")
  except KeyError:
    print("invalid choice")

if __name__ == '__main__':
  while True:
    human = input(f"{' '.join(choices)}? > ").lower()
    computer = choice(choices)
    round(human, computer)