class StateMachine:

def __init__(self):

self.handlers = {} # 状态转移函数字典

self.startState = None # 初始状态

self.endState = [] # 最终状态集合

# 参数name为状态名,handler为状态转移函数,end_state表明是否为最终状态

def add_state(self, name, handler, end_state=0):

name = name.upper()

self.handlers[name] = handler

if end_state:

self.endState.append(name)

def set_start(self, name):

self.startState = name.upper()

def run(self, cargo):

try:

handler = self.handlers[self.startState]

except:

raise Exception("must call .set_start() before .run()")

if not self.endState:

raise Exception("at least one state must be an end_state")

while True:

(newState, cargo) = handler(cargo)

if newState.upper() in self.endState:

print("reached ", newState)

break

else:

handler = self.handlers[newState.upper()]

# 有限状态集合

positive_adjectives = ["great", "super", "fun", "entertaining", "easy"]

negative_adjectives = ["boring", "difficult", "ugly", "bad"]

# 自定义状态转变函数

def start_transitions(txt):

# 用指定分隔符对字符串进行切片,默认为空格分割,参数num指定分割次数

# 将"Python is XXX"语句分割为"Python"和之后的"is XXX"

splitted_txt = txt.split(None, 1)

word, txt = splitted_txt if len(splitted_txt) > 1 else (txt, "")

if word == "Python":

newState = "Python_state" # 如果第一个词是Python则可转换到"Python状态"

else:

newState = "error_state" # 如果第一个词不是Python则进入终止状态

return (newState, txt) # 返回新状态和余下的语句txt

def python_state_transitions(txt):

splitted_txt = txt.split(None, 1)

word, txt = splitted_txt if len(splitted_txt) > 1 else (txt, "")

if word == "is":

newState = "is_state"

else:

newState = "error_state"

return (newState, txt)

def is_state_transitions(txt):

splitted_txt = txt.split(None, 1)

word, txt = splitted_txt if len(splitted_txt) > 1 else (txt, "")

if word == "not":

newState = "not_state"

elif word in positive_adjectives:

newState = "pos_state"

elif word in negative_adjectives:

newState = "neg_state"

else:

newState = "error_state"

return (newState, txt)

def not_state_transitions(txt):

splitted_txt = txt.split(None, 1)

word, txt = splitted_txt if len(splitted_txt) > 1 else (txt, "")

if word in positive_adjectives:

newState = "neg_state"

elif word in negative_adjectives:

newState = "pos_state"

else:

newState = "error_state"

return (newState, txt)

if __name__ == "__main__":

m = StateMachine()

m.add_state("Start", start_transitions) # 添加初始状态

m.add_state("Python_state", python_state_transitions)

m.add_state("is_state", is_state_transitions)

m.add_state("not_state", not_state_transitions)

m.add_state("neg_state", None, end_state=1) # 添加最终状态

m.add_state("pos_state", None, end_state=1)

m.add_state("error_state", None, end_state=1)

m.set_start("Start") # 设置开始状态

m.run("Python is great")

m.run("Python is not fun")

m.run("Perl is ugly")

m.run("Pythoniseasy")