Question

from MyStack import MyStack

def infixToPostfix(infixexpr):

   prec = {}

   prec["*"] = 3

   prec["/"] = 3

   prec["+"] = 2

   prec["-"] = 2

   prec["("] = 1

   opStack = Stack()

   postfixList = []

   tokenList = infixexpr.split()

   for token in tokenList:

       if token in "ABCDEFGHIJKLMNOPQRSTUVWXYZ" or token in "0123456789":

           postfixList.append(token)

       elif token in prec:

       op_2=operand_stack.peek()

       operand_stack.pop()

       op_1=operand_stack.peek()

       operand_stack.pop()

       operand_stack.push("("+op_1+token+op_2+")")

   temporary_list.append(operand_stack.pop())

   for i in temporary_list[0]:

       infix_list.append(i)

   return " ".join(infix_list)

print(postfix_to_infix("3 6 7*+"))

def doMath(op, op1, op2):

  if op == "*":

      return op1 * op2

  elif op == "/":

      return op1 / op2

  elif op == "+":

      return op1 + op2

  else:

      return op1 - op2

def infixEval(expr):

   operandStack=MyStack()

   operatorStack=MyStack

   tokenList=expr.split()

   for token in tokenList:

       if token in "1234567890":

           operandStack.push(int(token))

       elif token in"*/+-":

           operatorStack.push(int(token))

       elif token== "(":

           continue

       elif token==")":

           operand2=operandStack.pop()

           operand1=operandStack.pop()

           operator=operatorStack.pop()

           result=doMath(operator,operand1, operand2)

           operandStack.push(result)

   return operandStack.pop()

print(infixEval("(3+(8*1))"))

Turn this direct infix evaluator from the above problem into a calculator.

Python

Answer 1

def calc():

  print("Select an operation.")

  print("1.Add , 2.Subtract , 3.Multiply , 4.Divide")

  while True:

      # Take input

    choice = input("Enter your choice of operation (1/2/3/4): ")

      # Check whether the choice is one of the defined options

    if (choice in ('1', '2', '3', '4')):

      num1 = float(input("Enter first number: "))

      num2 = float(input("Enter second number: "))

      num1 = str(num1)

      num2 = str(num2)

      if (choice == '1'):

        print(infixEval(num1+"+"+num2))

      elif choice == '2':

        print(infixEval(num1+"-"+num2))

        

      elif choice == '3':

        print(infixEval(num1+"*"+num2))

      elif choice == '4':

        print(infixEval(num1+"/"+num2))

      break

    else :

      print("Invalid Input")

calc()