from axelrod.action import Action
from axelrod.player import Player
C, D = Action.C, Action.D
[docs]class Inverse(Player):
"""A player who defects with a probability that diminishes relative to how
long ago the opponent defected.
Names:
- Inverse: Original Name by Karol Langner
"""
name = "Inverse"
classifier = {
"memory_depth": float("inf"), # Long memory
"stochastic": True,
"long_run_time": False,
"inspects_source": False,
"manipulates_source": False,
"manipulates_state": False,
}
[docs] def strategy(self, opponent: Player) -> Action:
"""Looks at opponent history to see if they have defected.
If so, player defection is inversely proportional to when this occurred.
"""
# calculate how many turns ago the opponent defected
index = next(
(
index
for index, value in enumerate(opponent.history[::-1], start=1)
if value == D
),
None,
)
if index is None:
return C
return self._random.random_choice(1 - 1 / abs(index))