title: TypeError: unbound method must be called with instance as first argument (got int instance instead) in Python 2
body: <p>In python 3 the following set of codes works, I wonder why in python 2.7 it gives me a TypeError: unbound method add() must be called with calc instance as first argument(got int instance instead)? how do I resolve this in Python 2.7?</p>
  
  <pre><code>class calc:
      def add(x,y):
          answer = x + y
          print(answer)
  
      def sub(x,y):
          answer = x - y
          print(answer)
  
      def mult(x,y):
          answer = x * y
          print(answer)
  
      def div(x,y):
          answer = x / y
          print(answer)
  
  calc.add(5, 7)
  </code></pre>