[python] python实现2048游戏，及代码解析。

　　我初学python，有不对之处望大家指教。转载请征得同意。

　　我在网络上也找了一些2048游戏代码的讲解，但都不是特别详细。所以我希望能够尽量详细的讲解。同时，有的地方我也不懂，希望大家能帮助补充。我会随时更新以方便后来者。

　　当然，需要一定的python基础再看此实例。

 #-*- coding:utf-8 -*-
 
 import curses
 from random import randrange, choice
 from collections import defaultdict
 # 引入3个扩展包
 
 letter_codes = [ord(ch) for ch in 'WASDRQwasdrq']
 actions = ['Up', 'Left', 'Down', 'Right', 'Restart', 'Exit']
 actions_dict = dict(zip(letter_codes, actions * 2))
 # 创建我们将要用的键盘输入字典，这个字典将在后边通过第18行的
 # keyboard.getch()
 # 而这个方法被封装成一个函数，调用函数以实现该方法。
 
 def get_user_action(keyboard):
     char = "N"
     while char not in actions_dict:
         char = keyboard.getch()
     return actions_dict[char]
 # 键盘输入以匹配字典的方法
 
 def transpose(field):
     return [list(row) for row in zip(*field)]
 # 矩阵转置，
 # 这是一个数学方法，如望详细了解，请先了解矩阵
 # 对于初学者，比较推荐暂时忽略。
 
 def invert(field):
     return [row[::-1] for row in field]
 # 矩阵逆转，同上
 
 class GameField(object):
     def __init__(self, height=4, width=4, win=2048):
         self.height = height
         self.width = width
         self.win_value = 2048
         self.score = 0
         self.highscore = 0
         self.reset()
     # 定义类的__init__方法，为初始化方法
 
     def reset(self):
         if self.score > self.highscore:
             self.highscore = self.score
         self.score = 0
         self.field = [[0 for i in range(self.width)] for j in range(self.height)]
         self.spawn()
         self.spawn()
     # 重置方法，虽然命名为reset，但是初始化也同样使用该方法。
     # 如果你觉得命名为set更合适，请改为set。
     # 这个方法中使用了spawn()函数，这个函数放在了后边，
     # spawn()函数的功能是生成新的数字，reset()需要生成两次。
 
     def move(self, direction):
     # 最重要的3个函数之一
         def move_row_left(row):
             def tighten(row):
                 new_row = [i for i in row if i != 0]
                 new_row += [0 for i in range(len(row) - len(new_row))]
                 return new_row
 
             def merge(row):
                 pair = False
                 new_row = []
                 for i in range(len(row)):
                     if pair:
                         new_row.append(2 * row[i])
                         self.score += 2 * row[i]
                         pair = False
                     else:
                         if i + 1 < len(row) and row[i] == row[i + 1]:
                             pair = True
                             new_row.append(0)
                         else:
                             new_row.append(row[i])
                 assert len(new_row) == len(row)
                 return new_row
             return tighten(merge(tighten(row)))
         #这里可以有不同的写法，就是tighten一次，merge一次。在merge的时候没必要加0了。
         # 欢迎大家把好的方法发给我，谢谢。http://www.cnblogs.com/danjawwi/
         # def merge(row):
         #     pair = False
         #     new_row = []
         #     for i in range(len(row)):
         #         if pair:
         #             new_row.append(2 * row[i])
         #             self.score += 2 * row[i]
         #             pair = False
         #         else:
         #             if i + 1 < len(row) and row[i] == row[i + 1]:
         #                 pair = True
         #             else:
         #                 new_row.append(row[i])
         #     new_row += [0 for j in range(len(row) - len(new_row))]
         #     return new_row
         #
         # return merge(tighten(row))
 
         moves = {}
         moves['Left']  = lambda field:                              \
                 [move_row_left(row) for row in field]
         moves['Right'] = lambda field:                              \
                 invert(moves['Left'](invert(field)))
         moves['Up']    = lambda field:                              \
                 transpose(moves['Left'](transpose(field)))
         moves['Down']  = lambda field:                              \
                 transpose(moves['Right'](transpose(field)))
         # 这里把row的迭代放在了方法外边，在对应字典值这里实现了。也可以放在方法里边
 
         if direction in moves:
             if self.move_is_possible(direction):
                 self.field = moves[direction](self.field)
                 self.spawn()
                 return True
             else:
                 return False
 
     def is_win(self):
         return any(any(i >= self.win_value for i in row) for row in self.field)
     #判断是否赢
 
     def is_gameover(self):
         return not any(self.move_is_possible(move) for move in actions)
     # 判断是否输
 
     def draw(self, screen):
     # 最重要的3个函数之一
         help_string1 = '(W)Up (S)Down (A)Left (D)Right'
         help_string2 = '     (R)Restart (Q)Exit'
         gameover_string = '           GAME OVER'
         win_string = '          YOU WIN!'
         def cast(string):
             screen.addstr(string + '\n')
 
         def draw_hor_separator():
             line = '+' + ('+------' * self.width + '+')[1:]
             #不明白为什么这里要这样写
             #直接line = '+------' * self.width + '+' 不行吗？
             #http://www.cnblogs.com/danjawwi/
 
             separator = defaultdict(lambda: line)
             if not hasattr(draw_hor_separator, "counter"):
                 draw_hor_separator.counter = 0
             cast(separator[draw_hor_separator.counter])
             draw_hor_separator.counter += 1
             #这里我也不明白，直接根据self.height输出不就行了？
 
         def draw_row(row):
             cast(''.join('|{: ^5} '.format(num) if num > 0 else '|      ' for num in row) + '|')
             #用到了join 和 format这两种方法。
         screen.clear()
         cast('SCORE: ' + str(self.score))
         if 0 != self.highscore:
             cast('HGHSCORE: ' + str(self.highscore))
         for row in self.field:
             draw_hor_separator()
             draw_row(row)
         draw_hor_separator()
         if self.is_win():
             cast(win_string)
         else:
             if self.is_gameover():
                 cast(gameover_string)
             else:
                 cast(help_string1)
         cast(help_string2)
 
     def spawn(self):
         new_element = 4 if randrange(100) > 89 else 2
         (i,j) = choice([(i,j) for i in range(self.width) for j in range(self.height) if self.field[i][j] == 0])
         self.field[i][j] = new_element
         #迭代器既可以根据层级来进行迭代，也可以在同层中迭代两次
 
     def move_is_possible(self, direction):
     # 最重要的3个函数之一
         def row_is_left_movable(row):
             def change(i):
                 if row[i] == 0 and row[i + 1] != 0:
                 # 这里是不是在说None != 0 ？
                     return True
                 if row[i] != 0 and row[i + 1] == row[i]:
                     return True
                 return False
             return any(change(i) for i in range(len(row) - 1))
 
         check = {}
         check['Left']  = lambda field:                              \
                 any(row_is_left_movable(row) for row in field)
 
         check['Right'] = lambda field:                              \
                  check['Left'](invert(field))
 
         check['Up']    = lambda field:                              \
                 check['Left'](transpose(field))
 
         check['Down']  = lambda field:                              \
                 check['Right'](transpose(field))
 
         if direction in check:
             return check[direction](self.field)
         else:
             return False
 
 def main(stdscr):
     def init():
         game_field.reset()
         return 'Game'
 
     def not_game(state):
         game_field.draw(stdscr)
         action = get_user_action(stdscr)
         responses = defaultdict(lambda: state)
         responses['Restart'], responses['Exit'] = 'Init', 'Exit'
         return responses[action]
 
     def game():
         game_field.draw(stdscr)
         action = get_user_action(stdscr)
 
         if action == 'Restart':
             return 'Init'
         if action == 'Exit':
             return 'Exit'
         if game_field.move(action):
             if game_field.is_win():
                 return 'Win'
             if game_field.is_gameover():
                 return 'Gameover'
         return 'Game'
 
     state_actions = {
             'Init': init,
             'Win': lambda: not_game('Win'),
             'Gameover': lambda: not_game('Gameover'),
             'Game': game
         }
 
     curses.use_default_colors()
     game_field = GameField(win=32)
 
     state = 'Init'
 
     while state != 'Exit':
         state = state_actions[state]()
 
 curses.wrapper(main)