input: Write a function to evaluate a postfix expression represented as a string. The function should split the expression into a list, use a stack to store integer values, and perform operations on the stack elements as specified by the operators in the expression. Finally, it should return the result of the expression as an integer.
  
  def evaluate(expression): 
    
      # split expression into list  
      expression = expression.split() 
    
      # stack to store integer values. 
      stack = []  
    
      # do for every element of expression. 
      for element in expression: 
    
          # If element is an operand push 
          # into stack it's a number only 
          if element.isdigit(): 
              stack.append(element) 
    
          # if element is an operator, 
          # pop two elements from stack 
          # perform respective operations 
          else:  
              val1 = stack.pop() 
              val2 = stack.pop() 
              stack.append(str(eval(val2 + element + val1))) 
    
      # return the value  
      return (int(stack[0])) 
  
  # Test cases
  assert evaluate("2 3 + 4 5 * *") == 46
  assert evaluate("3 4 + 2 * 7 -") == 7
  assert evaluate("5 3 4 * +") == 17
  assert evaluate("6 2 3 + - 3 8 2 / + * 2 ^ 3 +") == 52
  assert evaluate("7 8 + 3 2 + /") == 3
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)
              elif element == '^':
                  stack.append(val2 ** val1)
      return stack[0]