class NodeOpt:"""操作符节点"""def __init__(self, ch, precedence):self.ch = chself.precedence = precedenceclass AST:"""加减乘除任意组合的语法解析器"""# 操作符栈_operatorStack = []# 值栈_exprStack = []# 具体操作符节点left_range = NodeOpt(ch='(', precedence=-1)right_range = NodeOpt(ch=')', precedence=0)add = NodeOpt(ch='+', precedence=1)sub = NodeOpt(ch='-', precedence=1)mul = NodeOpt(ch='*', precedence=2)div = NodeOpt(ch='/', precedence=2)__opts = [add, sub, mul, div, left_range, right_range]def getOptNode(self, ch):"""根据符号获取节点"""for ops in self.__opts:if ops.ch == ch:return opsdef isValue(self, ch):"""判断是否为数值"""if self.isOperator(ch):return Falsereturn Truedef isOperator(self, ch):"""判断是否为操作符"""for ops in self.__opts:if ops.ch == ch:return Truereturn Falsedef operator(self, e1, e2, operator):"""执行操作"""opt = operator.che1 = float(e1)e2 = float(e2)if opt is '+':return e1 + e2elif opt is '-':return e1 - e2elif opt is '*':return e1 * e2elif opt is '/':return e1 / e2else:return Nonedef ifGo(self):if len(self._exprStack) >= 2 and len(self._operatorStack) >= 1:return Trueelse:return Falsedef parse(self, input):""":param input: 字符数组"""for ch in input:if ch is '(':ch = self.getOptNode(ch)self._operatorStack.append(ch)elif self.isValue(ch):self._exprStack.append(ch)elif self.isOperator(ch):ch = self.getOptNode(ch)while self.ifGo() and ch.precedence <= self._operatorStack[-1].precedence:e2 = self._exprStack.pop()e1 = self._exprStack.pop()operator = self._operatorStack.pop()self._exprStack.append(self.operator(e1, e2, operator))self._operatorStack.append(ch)if ch.ch is ')':while self._operatorStack[-1].ch != '(':self._operatorStack.pop()self._operatorStack.pop()else:return Exceptionwhile self.ifGo():e2 = self._exprStack.pop()e1 = self._exprStack.pop()operator = self._operatorStack.pop()self._exprStack.append(self.operator(e1, e2, operator))return self._exprStack.pop()if __name__ == '__main__':ast = AST()myopt = "2/(3+((2-5)+1))*(3-1)+6-8"optlist = []i = 0while i < len(myopt):optlist.append(myopt[i])i += 1result = ast.parse(optlist)print(result)