text: import os
  import sys
  import time
  import datetime
  import asyncio
  import logging  #.log
  
  #in module
  class cal():
      def __init__(self,a,b):
          self.a=a
          self.b=b
      def add(self):
          return self.a+self.b
      def mul(self):
          return self.a*self.b
      def div(self):
          return self.a/self.b
      def sub(self):
          return self.a-self.b
      
  
  def run():
      a=int(input("Enter first number: "))
      b=int(input("Enter second number: "))
      obj=cal(a,b)
      choice=1
      while choice!=0:
          print("0. Exit")
          print("1. Add")
          print("2. Subtraction")
          print("3. Multiplication")
          print("4. Division")
          choice=int(input("Enter choice: "))
          if choice==1:
              print("Result: ",obj.add())
          elif choice==2:
              print("Result: ",obj.sub())
          elif choice==3:
              print("Result: ",obj.mul())
          elif choice==4:
              print("Result: ",round(obj.div(),2))
          elif choice==0:
              print("Exiting!")
          else:
              print("Invalid choice!!")
      print()
  
  def log():
      logging.basicConfig(
          #filename='logger.log',filemode='a', 
          format='%(asctime)s - %(levelname)s - %(message)s', datefmt='%d-%b-%y %H:%M:%S',
          level=logging.DEBUG)
  
  #main functions  
  def main():
      log()
      run()
  
  
  if __name__ == '__main__':
      main()
  
  
  
  
  