解释器模式 python 表达式计算

import sys
class priority:#定义符号优先级
    symbol = '#+-*/%()'
    def getisp(self,a):#栈内优先权
        if '#'.find(a)!=-1: return 0
        if '('.find(a)!=-1: return 1
        if '-+'.find(a)!=-1: return 3
        if '*/%'.find(a)!=-1: return 5
        if ')'.find(a)!=-1: return 6
    def geticp(self,a): #栈外优先权
        if '#'.find(a)!=-1: return 0
        if '('.find(a)!=-1: return 6
        if '-+'.find(a)!=-1: return 2
        if '*/%'.find(a)!=-1: return 4
        if ')'.find(a)!=-1: return 1

class Expression:#抽象类
    def interpreter():
        pass

class VarExpression(Expression):#数字,终结表达式
    def __init__(self,_key):
        self.key=_key
    def interpreter(self):
        return self.key

class SymbolExpression(Expression):#运算类基类
    def __init__(self,_left,_right):
        self.left = _left
        self.right = _right

class SubExpression(SymbolExpression):#减
    def __init__(self,_left,_right):
        self.parent=SymbolExpression(_left,_right)
    def interpreter(self):
        return self.parent.left.interpreter()-self.parent.right.interpreter()

class AddExpression(SymbolExpression):#加
    def __init__(self,_left,_right):
        self.parent=SymbolExpression(_left,_right)
    def interpreter(self):
        return self.parent.left.interpreter()+self.parent.right.interpreter()

class MulExpression(SymbolExpression):#乘
    def __init__(self,_left,_right):
        self.parent=SymbolExpression(_left,_right)
    def interpreter(self):
        return self.parent.left.interpreter()*self.parent.right.interpreter()

class DivExpression(SymbolExpression):#除
    def __init__(self,_left,_right):
        self.parent=SymbolExpression(_left,_right)
    def interpreter(self):
        return self.parent.left.interpreter()/self.parent.right.interpreter()

class ModExpression(SymbolExpression):#取余
    def __init__(self,_left,_right):
        self.parent=SymbolExpression(_left,_right)
    def interpreter(self):
        return self.parent.left.interpreter()%self.parent.right.interpreter()

class Calculator:
    exp=''
    order=[]
    def __init__(self,_exp):
        _exp = _exp.replace(' ','')
        self.exp=_exp
        _exp=_exp+'#'
        i=0
        f=0
        p=1
        tmp = 0
        stack='#'
        order=[]
        pty = priority()
        while len(stack)>0:
            if pty.symbol.find(_exp[i])!=-1:
                if f>0:order = order+[tmp]
                f = 0
                p=1
                tmp = 0
                ch = _exp[i]
                ch1 = stack[-1]
                #print (ch1,' ',pty.getisp(ch1),' ',pty.geticp(ch))
                if pty.getisp(ch1)<pty.geticp(ch):
                    stack=stack+ch
                    i=i+1
                elif pty.getisp(ch1)>pty.geticp(ch):
                    order = order+[stack[-1]]
                    stack = stack[0:-1]
                else :
                    if stack[-1]=='(': i=i+1
                    stack = stack[0:-1]
            else :
                if f==0: f = 1
                if _exp[i]=='.':
                    f = 2
                elif f==1:
                    tmp = tmp*10 +int(_exp[i])-int('0')
                else:
                    p = p*0.1
                    tmp = tmp+(int(_exp[i])-int('0'))*p
                i=i+1
        print (order) #order 为后缀表达式
        self.order=order
        stack=[]
        for i in order:#创建递归树
            if pty.symbol.find(str(i))!=-1:
                right = stack[-1] # 把栈中连个元素取出
                left = stack[-2]
                stack = stack[0:-2]
                if '+'.find(str(i))!=-1:
                    stack = stack+[AddExpression(left,right)]
                elif '-'.find(str(i))!=-1:
                    stack = stack+[SubExpression(left,right)]
                elif '*'.find(str(i))!=-1:
                    stack = stack+[MulExpression(left,right)]
                elif '/'.find(str(i))!=-1:
                    stack = stack+[DivExpression(left,right)]
                elif '%'.find(str(i))!=-1:
                    stack = stack+[ModExpression(left,right)]
            else :
                stack=stack+[VarExpression(i)]
        self.expression = stack[0]
    
    def run(self):#计算递归树
        return self.expression.interpreter()
def Client():
    a=input("请输入正确表达式：eg:1*(2+3):\n")
    cal = Calculator(a)
    print (a,"=",cal.run())

Client()