from __future__ import print_function

class calcerr(ValueError):
    '''mistake'''
class oper2:
    def __init__(self,func,num_args=2):
        self.func=func
        self.num_args=num_args
class calc:
    def __init__(self):
        import operator as oper
        self.oper_list = {'+':oper2(oper.add),
                     "-":oper2(oper.sub),
                     "*":oper2(oper.mul),
                     "/":oper2(oper.truediv),
                     "^":oper2(oper.pow),
                     "%":oper2(oper.mod),
                     "abs":oper2(oper.abs,num_args=1),
                    }
        self.eval_q=[]
    def clear_q(self):
        self.eval_q=[]
    def print_q(self):
        print(self.eval_q)
    def add_custom(self,filename):
        import json
        with open(filename) as file:
            data=json.loads(file.read())
        import math
        for key,module in data.items():
            if hasattr(math, module):
                self.oper_list[key] = oper2(getattr(math, module), num_args=1)
    def addto_q(self,val):
        self.eval_q.append(self.convert_user(val))
        if self.isoperation(self.eval_q[-1]):
            result = self.eval_q.pop()
            num_args = self.oper_list[result].num_args
            if len(self.eval_q)<num_args:
                raise calcerr('not enough val')
            args = []
            for i in range(num_args):
                args.append(self.eval_q.pop())
            result = calc.perf_oper(result,args)
            self.eval_q.append(result)
    def print_oper(self):
        print('operations list:')
        for x in self.oper_list.keys():
            print(x,)
        print('')

    def isoperation(self,val):
         if val in self.oper_list.keys():
            return True
         else:
            return False

    def convert_user(self,value):
        if self.isfloat(value):
            return float(value)
        elif self.isoperation(value):
            return value
        else:
            raise calcerr('invalid')

    def perf_oper(self,op,val):
        if self.isoperation(op):
            return self.oper_list[op].func(*val)
        return op
    @staticmethod
    def isfloat(value):
        try:
            tmp = float(value)
            return True
        except ValueError:
            return False

print("calc")
calc =calc()
calc.add_custom("operators.json")
calc.print_oper()
while True:
    user = input("")
    if user == 'q':
        break
    try:
        calc.addto_q(user)
    except calcerr as Err:
        print('error', Err)
    calc.print_q()