Python mathematics within variable

My Python code needs to be able to randomly generate a number between 1 and 3 to determine what function to perform (addition, multiplication or subtraction). That works fine. I randomly generate two numbers and need to get this random function. So it would be like a basic maths sum like 3 + 6 = 9. The 3 would be stored as number1 (and randomly generated). The + would be stored as function and would also be randomly generated. The 6 would be stored as number2 and also randomly generated.

The problem I am having is combining all the variables together and getting it to work out the maths.

So I could do the following: (the numbers entered would have been randomly generated)

number1 = 3
number2 = 8
function = 3 (for the purposes of this: addition)

function then is changed to "+"

I am left doing this:

answer = number1, function, number2

Which obviously doesn't work.

Relevant full code:

from random import randint #Allows for random numbers
import time #Allows you to wait
year = int(input("What year are you? "))

if year == 6:
      #Do year 6 stuff
      year = "6"
      print("You are year", year)

      function = randint(1,3)

      if function == 1:
            function = "*"
            print("Multiplying")
      elif function == 2:
            function = "-"
            print("Subtracting")
      elif function == 3:
            function = "+"
            print("Addiding")
      else:
            print("Program did not work as intended, failed at function point.")

      tester = 300

      while tester > 20:
            number1 = randint(1,20)
            number2 = randint(1,20)
            int(tester) = number1 , function , number2

            time.sleep(2)

            print("Number1:",number1)
            print("Number2:",number2)
            print("Answer:",tester)



elif year == 5:
      #Do year 5 stuff
      year = "5"
      print("You are year", year)
elif year == 4:
      #Do year 4 stuff
      year = "4"
      print("You are year", year)
elif year == 3:
      #Do year 3 stuff
      year = "3"
      print("You are year", year)
elif year == 2:
      #Do year 2 stuff
      year = "2"
      print("You are year", year)
else:
      print("You do not classify for this quiz.")