state_legal_actions.md

OpenSpiel state methods: legal_actions

Back to Core API reference

1. legal_actions()
2. legal_actions(player: int)

Returns the list of legal actions (integers between 0 and game.num_distinct_actions() - 1) for (1) the current player, or (2) the specified player.

When called on a chance node, returns the legal chance outcomes without their corresponding probabilities.

When called on a simultaneous node, returns the set of legal joint actions represented as flat integers, which can then be passed to apply_action.

Examples:

import pyspiel

game = pyspiel.load_game("tic_tac_toe")
state = game.new_initial_state()
print(state.legal_actions())
# Output: [0, 1, 2, 3, 4, 5, 6, 7, 8]

game = pyspiel.load_game("matrix_pd")
state = game.new_initial_state()
print(state.legal_actions(0))   # row player
print(state.legal_actions(1))   # column player
# Output:
# [0, 1]
# [0, 1]