input: Write a function to evaluate a postfix expression. The input to the function should be a string with the postfix expression. The output should be the evaluated value of the expression.
  def evaluate(expression):
      expression = expression.split() 
      stack = [] 
      for element in expression: 
          if element.isdigit(): 
              stack.append(element) 
          else:  
              val1 = stack.pop() 
              val2 = stack.pop() 
              stack.append(str(eval(val2 + element + val1))) 
      return (int(stack[0])) 
  
  assert evaluate("2 3 + 4 5 * *")==46
  assert evaluate("5 3 2 + *")==25
  assert evaluate("10 2 8 * + 3 -")==23
  assert evaluate("9 3 / 5 +")==8
  assert evaluate("3 5 + 4 2 * +")==17
output: def evaluate(expression):
      expression = expression.split() 
      stack = [] 
      for element in expression: 
          if element.isdigit(): 
              stack.append(int(element)) 
          else:  
              val1 = stack.pop() 
              val2 = stack.pop() 
              if element == '+':
                  stack.append(val2 + val1)
              elif element == '-':
                  stack.append(val2 - val1)
              elif element == '*':
                  stack.append(val2 * val1)
              elif element == '/':
                  stack.append(val2 // val1)
      return stack[0]