Game Tree Navigation
The sente.game object records all of the moves played in a tree structure.
Sente provides utilities for navigating around this tree with the game.play(), game.step_up() and game.get_branches() methods.
Playing Stones
The game.play() method plays at a given point on the board.
>>> import sente
>>> game = sente.Game(9) # creates a 9x9 board
>>> game.play(4, 4) # plays a stone on the 4-4 point
>>> print(game)
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Undoing Moves
On the other hand, the game.step_up() method undoes the previous move played on the board.
>>> game = sente.Game(9)
>>> game.play(4, 4)
>>> game.step_up() # undo the previous move
>>> print(game)
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Repeatedly calling step_up() can be tedious and slow, so the number of steps that step_up() takes can be specified as an argument.
>>> game = sente.Game(9)
>>> game.play(4, 4)
>>> game.play(7, 7)
>>> game.play(4, 7)
>>> game.step_up(2) # undo two moves
>>> print(game)
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Another alternative to the step_up() method is the advance_to_root() method, which simply undoes every move in the game, leaving the board empty.
>>> game = sente.Game(9)
>>> game.play(4, 4)
>>> game.play(7, 7)
>>> game.play(4, 7)
>>> game.advance_to_root()
>>> print(game)
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Once moves have been undone, the move(s) played at a given tree node can be obtained using the get_branches() method.
>>> game = sente.Game(9)
>>> game.play(4, 4)
>>> game.play(7, 7)
>>> game.step_up()
>>> print(game.get_branches())
[<sente.Move W G6]
The sente.Move object is an object that can be passed to the game.play() method to play the specified move.
The get_branches() method returns a python list containing all of the moves played at the current nod.
>>> game = sente.Game(9)
>>> game.play(4, 4)
>>> game.play(7, 7)
>>> game.step_up()
>>> branches = game.get_branches()
>>> game.play(branches[0])
>>> print(game)
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If multiple branches exist from the current node, then get_branches() will return a list containing all of them.
Move Comments
Each node of the Game tree is allowed to have a “comment” associated with it.
These comments typically include commentary on the game and can also include messages sent by the players during the game.
The comment associated with the current node can be accessed through the comment attribute.
>>> game = sente.Game()
>>> game.comment = "the start of the game"
>>> print(game.comment)
the start of the game
>>> game.play(4, 4)
>>> print(game.comment) # the comment from the start of the game is still stored,
>>> game.comment = "the first move of the game"
>>> print(game.comment)
the first move of the game
>>> game.step_up()
>>> print(game.comment)
the start of the game
Move Sequences
When undoing moves in sente, it can be tricky to keep track of the sequence of moves that leads to a given board position.
To make game tree navigation more straightforward, the sente.Game Object contains a method called get_sequence that generates a python list containing the sequence of moves that have been played in the game so far.
>>> game.play(4, 4)
>>> game.play(4, 15)
>>> game.play(15, 15)
>>> print(game.get_sequence())
[<sente.Move B[dd]>, <sente.Move W[do]>, <sente.Move B[oo]>]
If the moves in a sequence are undone, the board position can be restored by using the play_sequence() method.
>>> print(game)
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>>> move_sequence = game.get_sequence()
>>> game.step_up(3) # alternatively, you could use the advance_to_root() method
>>> game.play_sequence(move_sequence)
>>> print(game)
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Additionally, because the get_sequence method returns a python list, python list slicing is supported.
>>> game.play(4, 4)
>>> game.play(4, 15)
>>> game.play(15, 15)
>>> print(game.get_sequence())
[<sente.Move B D4>, <sente.Move W D15>, <sente.Move B P15>]
>>> print(game)
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>>> move_sequence = game.get_sequence()
>>> game.step_up(3) # alternatively, you could use the advance_to_root() method
>>> game.play_sequence(move_sequence[:-1])
>>> print(game)
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