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纯Python实现人工智能_python ai

python ai

很久以前微信流行过一个小游戏:打飞机,这个游戏简单又无聊。在2017年来临之际,我就实现一个超级弱智的人工智能(AI),这货可以躲避从屏幕上方飞来的飞机。本帖只使用纯Python实现,不依赖任何高级库。

本文的AI基于neuro-evolution,首先简单科普一下neuro-evolution。从neuro-evolution这个名字就可以看出它由两部分组成-neuro and evolution,它是使用进化算法(遗传算法是进化算法的一种)提升人工神经网络的机器学习技术,其实就是用进化算法改进并选出最优的神经网络。如果你觉得这篇文章看起来稍微还有些吃力,或者想要系统地学习人工智能,那么推荐你去看床长人工智能教程。非常棒的大神之作,教程不仅通俗易懂,而且很风趣幽默。点击这里可以查看教程。

neuro-evolution

定义一些变量:


  
  
  1. import math
  2. import random
  3. # 神经网络3层, 1个隐藏层; 4个input和1个output
  4. network = [ 4, [ 16], 1]
  5. # 遗传算法相关
  6. population = 50
  7. elitism = 0.2
  8. random_behaviour = 0.1
  9. mutation_rate = 0.5
  10. mutation_range = 2
  11. historic = 0
  12. low_historic = False
  13. score_sort = -1
  14. n_child = 1
  • 1

 

定义神经网络:

 


  
  
  1. # 激活函数
  2. def sigmoid(z):
  3. return 1.0/( 1.0+math.exp(-z))
  4. # random number
  5. def random_clamped():
  6. return random.random()* 2 -1
  7. # "神经元"
  8. class Neuron():
  9. def __init__(self):
  10. self.biase = 0
  11. self.weights = []
  12. def init_weights(self, n):
  13. self.weights = []
  14. for i in range(n):
  15. self.weights.append(random_clamped())
  16. def __repr__(self):
  17. return 'Neuron weight size:{} biase value:{}'.format(len(self.weights), self.biase)
  18. # 层
  19. class Layer():
  20. def __init__(self, index):
  21. self.index = index
  22. self.neurons = []
  23. def init_neurons(self, n_neuron, n_input):
  24. self.neurons = []
  25. for i in range(n_neuron):
  26. neuron = Neuron()
  27. neuron.init_weights(n_input)
  28. self.neurons.append(neuron)
  29. def __repr__(self):
  30. return 'Layer ID:{} Layer neuron size:{}'.format(self.index, len(self.neurons))
  31. # 神经网络
  32. class NeuroNetwork():
  33. def __init__(self):
  34. self.layers = []
  35. # input:输入层神经元数 hiddens:隐藏层 output:输出层神经元数
  36. def init_neuro_network(self, input, hiddens , output):
  37. index = 0
  38. previous_neurons = 0
  39. # input
  40. layer = Layer(index)
  41. layer.init_neurons(input, previous_neurons)
  42. previous_neurons = input
  43. self.layers.append(layer)
  44. index += 1
  45. # hiddens
  46. for i in range(len(hiddens)):
  47. layer = Layer(index)
  48. layer.init_neurons(hiddens[i], previous_neurons)
  49. previous_neurons = hiddens[i]
  50. self.layers.append(layer)
  51. index += 1
  52. # output
  53. layer = Layer(index)
  54. layer.init_neurons(output, previous_neurons)
  55. self.layers.append(layer)
  56. def get_weights(self):
  57. data = { 'network':[], 'weights':[] }
  58. for layer in self.layers:
  59. data[ 'network'].append(len(layer.neurons))
  60. for neuron in layer.neurons:
  61. for weight in neuron.weights:
  62. data[ 'weights'].append(weight)
  63. return data
  64. def set_weights(self, data):
  65. previous_neurons = 0
  66. index = 0
  67. index_weights = 0
  68. self.layers = []
  69. for i in data[ 'network']:
  70. layer = Layer(index)
  71. layer.init_neurons(i, previous_neurons)
  72. for j in range(len(layer.neurons)):
  73. for k in range(len(layer.neurons[j].weights)):
  74. layer.neurons[j].weights[k] = data[ 'weights'][index_weights]
  75. index_weights += 1
  76. previous_neurons = i
  77. index += 1
  78. self.layers.append(layer)
  79. # 输入游戏环境中的一些条件(如敌机位置), 返回要执行的操作
  80. def feed_forward(self, inputs):
  81. for i in range(len(inputs)):
  82. self.layers[ 0].neurons[i].biase = inputs[i]
  83. prev_layer = self.layers[ 0]
  84. for i in range(len(self.layers)):
  85. # 第一层没有weights
  86. if i == 0:
  87. continue
  88. for j in range(len(self.layers[i].neurons)):
  89. sum = 0
  90. for k in range(len(prev_layer.neurons)):
  91. sum += prev_layer.neurons[k].biase * self.layers[i].neurons[j].weights[k]
  92. self.layers[i].neurons[j].biase = sigmoid(sum)
  93. prev_layer = self.layers[i]
  94. out = []
  95. last_layer = self.layers[ -1]
  96. for i in range(len(last_layer.neurons)):
  97. out.append(last_layer.neurons[i].biase)
  98. return out
  99. def print_info(self):
  100. for layer in self.layers:
  101. print(layer)
  • 1

遗传算法:


  
  
  1. # "基因组"
  2. class Genome():
  3. def __init__(self, score, network_weights):
  4. self.score = score
  5. self.network_weights = network_weights
  6. class Generation():
  7. def __init__(self):
  8. self.genomes = []
  9. def add_genome(self, genome):
  10. i = 0
  11. for i in range(len(self.genomes)):
  12. if score_sort < 0:
  13. if genome.score > self.genomes[i].score:
  14. break
  15. else:
  16. if genome.score < self.genomes[i].score:
  17. break
  18. self.genomes.insert(i, genome)
  19. # 杂交+突变
  20. def breed(self, genome1, genome2, n_child):
  21. datas = []
  22. for n in range(n_child):
  23. data = genome1
  24. for i in range(len(genome2.network_weights[ 'weights'])):
  25. if random.random() <= 0.5:
  26. data.network_weights[ 'weights'][i] = genome2.network_weights[ 'weights'][i]
  27. for i in range(len(data.network_weights[ 'weights'])):
  28. if random.random() <= mutation_rate:
  29. data.network_weights[ 'weights'][i] += random.random() * mutation_range * 2 - mutation_range
  30. datas.append(data)
  31. return datas
  32. # 生成下一代
  33. def generate_next_generation(self):
  34. nexts = []
  35. for i in range(round(elitism*population)):
  36. if len(nexts) < population:
  37. nexts.append(self.genomes[i].network_weights)
  38. for i in range(round(random_behaviour*population)):
  39. n = self.genomes[ 0].network_weights
  40. for k in range(len(n[ 'weights'])):
  41. n[ 'weights'][k] = random_clamped()
  42. if len(nexts) < population:
  43. nexts.append(n)
  44. max_n = 0
  45. while True:
  46. for i in range(max_n):
  47. childs = self.breed(self.genomes[i], self.genomes[max_n], n_child if n_child > 0 else 1)
  48. for c in range(len(childs)):
  49. nexts.append(childs[c].network_weights)
  50. if len(nexts) >= population:
  51. return nexts
  52. max_n += 1
  53. if max_n >= len(self.genomes) -1:
  54. max_n = 0
  • 1

NeuroEvolution:


  
  
  1. class Generations():
  2. def __init__(self):
  3. self.generations = []
  4. def first_generation(self):
  5. out = []
  6. for i in range(population):
  7. nn = NeuroNetwork()
  8. nn.init_neuro_network(network[ 0], network[ 1], network[ 2])
  9. out.append(nn.get_weights())
  10. self.generations.append(Generation())
  11. return out
  12. def next_generation(self):
  13. if len(self.generations) == 0:
  14. return False
  15. gen = self.generations[ -1].generate_next_generation()
  16. self.generations.append(Generation())
  17. return gen
  18. def add_genome(self, genome):
  19. if len(self.generations) == 0:
  20. return False
  21. return self.generations[ -1].add_genome(genome)
  22. class NeuroEvolution():
  23. def __init__(self):
  24. self.generations = Generations()
  25. def restart(self):
  26. self.generations = Generations()
  27. def next_generation(self):
  28. networks = []
  29. if len(self.generations.generations) == 0:
  30. networks = self.generations.first_generation()
  31. else:
  32. networks = self.generations.next_generation()
  33. nn = []
  34. for i in range(len(networks)):
  35. n = NeuroNetwork()
  36. n.set_weights(networks[i])
  37. nn.append(n)
  38. if low_historic:
  39. if len(self.generations.generations) >= 2:
  40. genomes = self.generations.generations[len(self.generations.generations) - 2].genomes
  41. for i in range(genomes):
  42. genomes[i].network = None
  43. if historic != -1:
  44. if len(self.generations.generations) > historic+ 1:
  45. del self.generations.generations[ 0:len(self.generations.generations)-(historic+ 1)]
  46. return nn
  47. def network_score(self, score, network):
  48. self.generations.add_genome(Genome(score, network.get_weights()))
  • 1

是AI就躲个飞机


  
  
  1. import pygame
  2. import sys
  3. from pygame.locals import *
  4. import random
  5. import math
  6. import neuro_evolution
  7. BACKGROUND = ( 200, 200, 200)
  8. SCREEN_SIZE = ( 320, 480)
  9. class Plane():
  10. def __init__(self, plane_image):
  11. self.plane_image = plane_image
  12. self.rect = plane_image.get_rect()
  13. self.width = self.rect[ 2]
  14. self.height = self.rect[ 3]
  15. self.x = SCREEN_SIZE[ 0]/ 2 - self.width/ 2
  16. self.y = SCREEN_SIZE[ 1] - self.height
  17. self.move_x = 0
  18. self.speed = 2
  19. self.alive = True
  20. def update(self):
  21. self.x += self.move_x * self.speed
  22. def draw(self, screen):
  23. screen.blit(self.plane_image, (self.x, self.y, self.width, self.height))
  24. def is_dead(self, enemes):
  25. if self.x < -self.width or self.x + self.width > SCREEN_SIZE[ 0]+self.width:
  26. return True
  27. for eneme in enemes:
  28. if self.collision(eneme):
  29. return True
  30. return False
  31. def collision(self, eneme):
  32. if not (self.x > eneme.x + eneme.width or self.x + self.width < eneme.x or self.y > eneme.y + eneme.height or self.y + self.height < eneme.y):
  33. return True
  34. else:
  35. return False
  36. def get_inputs_values(self, enemes, input_size=4):
  37. inputs = []
  38. for i in range(input_size):
  39. inputs.append( 0.0)
  40. inputs[ 0] = (self.x* 1.0 / SCREEN_SIZE[ 0])
  41. index = 1
  42. for eneme in enemes:
  43. inputs[index] = eneme.x* 1.0 / SCREEN_SIZE[ 0]
  44. index += 1
  45. inputs[index] = eneme.y* 1.0 / SCREEN_SIZE[ 1]
  46. index += 1
  47. #if len(enemes) > 0:
  48. #distance = math.sqrt(math.pow(enemes[0].x + enemes[0].width/2 - self.x + self.width/2, 2) + math.pow(enemes[0].y + enemes[0].height/2 - self.y + self.height/2, 2));
  49. if len(enemes) > 0 and self.x < enemes[ 0].x:
  50. inputs[index] = -1.0
  51. index += 1
  52. else:
  53. inputs[index] = 1.0
  54. return inputs
  55. class Enemy():
  56. def __init__(self, enemy_image):
  57. self.enemy_image = enemy_image
  58. self.rect = enemy_image.get_rect()
  59. self.width = self.rect[ 2]
  60. self.height = self.rect[ 3]
  61. self.x = random.choice(range( 0, int(SCREEN_SIZE[ 0] - self.width/ 2), 71))
  62. self.y = 0
  63. def update(self):
  64. self.y += 6
  65. def draw(self, screen):
  66. screen.blit(self.enemy_image, (self.x, self.y, self.width, self.height))
  67. def is_out(self):
  68. return True if self.y >= SCREEN_SIZE[ 1] else False
  69. class Game():
  70. def __init__(self):
  71. pygame.init()
  72. self.screen = pygame.display.set_mode(SCREEN_SIZE)
  73. self.clock = pygame.time.Clock()
  74. pygame.display.set_caption( '是AI就躲个飞机')
  75. self.ai = neuro_evolution.NeuroEvolution()
  76. self.generation = 0
  77. self.max_enemes = 1
  78. # 加载飞机、敌机图片
  79. self.plane_image = pygame.image.load( 'plane.png').convert_alpha()
  80. self.enemy_image = pygame.image.load( 'enemy.png').convert_alpha()
  81. def start(self):
  82. self.score = 0
  83. self.planes = []
  84. self.enemes = []
  85. self.gen = self.ai.next_generation()
  86. for i in range(len(self.gen)):
  87. plane = Plane(self.plane_image)
  88. self.planes.append(plane)
  89. self.generation += 1
  90. self.alives = len(self.planes)
  91. def update(self, screen):
  92. for i in range(len(self.planes)):
  93. if self.planes[i].alive:
  94. inputs = self.planes[i].get_inputs_values(self.enemes)
  95. res = self.gen[i].feed_forward(inputs)
  96. if res[ 0] < 0.45:
  97. self.planes[i].move_x = -1
  98. elif res[ 0] > 0.55:
  99. self.planes[i].move_x = 1
  100. self.planes[i].update()
  101. self.planes[i].draw(screen)
  102. if self.planes[i].is_dead(self.enemes) == True:
  103. self.planes[i].alive = False
  104. self.alives -= 1
  105. self.ai.network_score(self.score, self.gen[i])
  106. if self.is_ai_all_dead():
  107. self.start()
  108. self.gen_enemes()
  109. for i in range(len(self.enemes)):
  110. self.enemes[i].update()
  111. self.enemes[i].draw(screen)
  112. if self.enemes[i].is_out():
  113. del self.enemes[i]
  114. break
  115. self.score += 1
  116. print( "alive:{}, generation:{}, score:{}".format(self.alives, self.generation, self.score), end= '\r')
  117. def run(self, FPS=1000):
  118. while True:
  119. for event in pygame.event.get():
  120. if event.type == QUIT:
  121. pygame.quit()
  122. sys.exit()
  123. self.screen.fill(BACKGROUND)
  124. self.update(self.screen)
  125. pygame.display.update()
  126. self.clock.tick(FPS)
  127. def gen_enemes(self):
  128. if len(self.enemes) < self.max_enemes:
  129. enemy = Enemy(self.enemy_image)
  130. self.enemes.append(enemy)
  131. def is_ai_all_dead(self):
  132. for plane in self.planes:
  133. if plane.alive:
  134. return False
  135. return True
  136. game = Game()
  137. game.start()
  138. game.run()
  • 1

 

AI的工作逻辑

 

假设你是AI,你首先繁殖一个种群(50个个体),开始的个体大都是歪瓜裂枣(上来就被敌机撞)。但是,即使是歪瓜裂枣也有表现好的,在下一代,你会使用这些表现好的再繁殖一个种群,经过代代相传,存活下来的个体会越来越优秀。其实就是仿达尔文进化论,种群->自然选择->优秀个体->杂交、变异->种群->循环n世代。ai开始时候的表现:

经过几百代之后,ai开始娱乐的躲飞机.

 

 

 

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