2048 in Python

A simple implementation of the game 2048 in Python, using ncurses.

It supports different “bases” (other than 2) as well as colors, and uses a kind of Python-y functional style.

Minus comments, the whole thing is 70 lines.

#-----------------------------functional-helpers-------------------------#

from functools import reduce, partial

def compose(*funcs):

  """
  Mathematical function composition.
  compose(h, g, f)(x) => h(g(f(x)))
  """

  return reduce(lambda a,e: lambda x: a(e(x)), funcs, lambda x: x)

#-----------------------------------base---------------------------------#

# The base determines three things:
#  - The number of squares which need to be in a row to coalesce (= base)
#  - The length of the side of the board (= base^2)
#  - The number added to a random blank box on the board at the beginning
#    of every turn. (The seed) (90% of the time, the number added will be
#    the base, but 10% of the time, it will be the square of the base)
#  - The number of seeds added at evey turn (= 2^(base - 2))
#
# Normal 2048 has a base of 2.

base = int(input("Choose a base. (2 for normal 2048)\n> "))

#-----------------------------------rand---------------------------------#

def addn(board):

  """
  Inserts n seeds into random, empty positions in board. Returns board.
  n = 2^(base - 2)
  The  seed is equal to base 90% of the time. 10% of the time, it is
  equal to the square of the base.
  """

  from random import randrange, sample

  inds    = range(base**2)
  empties = [(y,x) for y in inds for x in inds if not board[y][x]]
  for y,x in sample(empties,2**(base-2)):
    board[y][x] = base if randrange(10) else base**2
  return board

#----------------------------------squish--------------------------------#

from itertools import count, groupby, starmap

def squish(row):

  """
  Returns a list, the same length as row, with the contents
  "squished" by the rules of 2048.
  Boxes are coalesced by adding their values together.
  Boxes will be coalesced iff:
   - They are adjacent, or there are only empty boxes between them.
   - The total number of boxes is equal to the base.
   - All the values of the boxes are equal.
  For base 2:
  [2][2][ ][ ] -> [4][ ][ ][ ]
  [2][2][2][2] -> [4][4][ ][ ]
  [4][ ][4][2] -> [8][2][ ][ ]
  [4][2][4][2] -> [4][2][4][2]
  For base 3:
  [3][ ][ ][3][ ][ ][3][ ][ ] -> [9][ ][ ][ ][ ][ ][ ][ ][ ]
  [3][3][3][3][3][3][3][3][3] -> [9][9][9][ ][ ][ ][ ][ ][ ]
  [3][3][3][9][9][ ][ ][ ][ ] -> [9][9][9][ ][ ][ ][ ][ ][ ]
  Keyword arguments:
  row -- A list, containing a combination of numbers and None
  (representing empty boxes)
  """

  r = []
  for n,x in starmap(lambda n, a: (n, sum(map(bool,a))),
                     groupby(filter(bool, row))):
    r += ([n*base] * (x//base)) + ([n] * (x%base))
  return r + ([None] * (base**2 - len(r)))

#----------------------------matrix-manipulation-------------------------#

# Transposes an iterable of iterables
# [[1, 2], -> [[1, 3],
#  [3, 4]]     [2, 4]]

def transpose(l): return [list(x) for x in zip(*l)]

# Flips horizontally an iterable of lists
# [[1, 2], -> [[2, 1],
#  [3, 4]]     [4, 3]]

flip = partial(map, reversed)

# transforms an iterable of iterables into a list of lists

thunk = compose(list, partial(map, list))

#----------------------------------moves---------------------------------#

# The move functions take a board as their argument, and return the board
# "squished" in a given direction.

moveLeft  = compose(thunk, partial(map, squish), thunk)
moveRight = compose(thunk, flip, moveLeft, flip)
moveUp    = compose(transpose, moveLeft, transpose)
moveDown  = compose(transpose, moveRight, transpose)

#-------------------------------curses-init------------------------------#

import curses

screen = curses.initscr()
curses.noecho()           # Don't print pressed keys
curses.cbreak()           # Don't wait for enter
screen.keypad(True)
curses.curs_set(False)    # Hide cursor

#----------------------------------keymap--------------------------------#

# A map from the arrow keys to the movement functions

moves = {curses.KEY_RIGHT: moveRight,
         curses.KEY_LEFT : moveLeft ,
         curses.KEY_UP   : moveUp   ,
         curses.KEY_DOWN : moveDown }

#----------------------------------color---------------------------------#

curses.start_color()
curses.use_default_colors()
curses.init_pair(1, curses.COLOR_WHITE, -1) # Border color

def colorfac():

  """Initializes a color pair and returns it (skips black)"""

  for i,c in zip(count(2),(c for c in count(1) if c!=curses.COLOR_BLACK)):
    curses.init_pair(i, c, -1)
    yield curses.color_pair(i)

colorgen = colorfac()

from collections import defaultdict

# A cache of colors, with the keys corresponding to numbers on the board.

colors = defaultdict(lambda: next(colorgen))

#---------------------------printing-the-board---------------------------#

size = max(11 - base*2, 3) # box width

def printBoard(board):

  def line(b,c): return b + b.join([c*(size)]*len(board)) + b
  border, gap = line("+","-"), line("|"," ")
  pad = "\n" + "\n".join([gap]*((size-2)//4)) if size > 5 else ""
  screen.addstr(0, 0, border, curses.color_pair(1))
  for row in board:
    screen.addstr(pad + "\n|", curses.color_pair(1))
    for e in row:
      if e: screen.addstr(str(e).center(size), colors[e])
      else: screen.addstr(" " * size)
      screen.addstr("|", curses.color_pair(1))
    screen.addstr(pad + "\n" + border, curses.color_pair(1))

#----------------------------------board---------------------------------#

# The board is a list of n lists, each of length n, where n is the base
# squared. Empty boxes are represented by None. The starting board has
# one seed.

board = addn([[None for _ in range(base**2)] for _ in range(base**2)])
printBoard(board)

#--------------------------------game-loop-------------------------------#

# The main game loop. Continues until there are not enough empty spaces
# on the board, or "q" is pressed.

for char in filter(moves.__contains__, iter(screen.getch, ord("q"))):
  moved = moves[char](board)
  if sum(not n for r in moved for n in r) < 2**(base-2): break
  if moved != board: board = addn(moved)
  printBoard(board)

#--------------------------------clean-up--------------------------------#

curses.nocbreak()     # Wait for enter
screen.keypad(0)      # Stop arrow-key handling
curses.echo()         # Print all keyboard input
curses.curs_set(True) # Show cursor
curses.endwin()       # Return to normal prompt