title: python - overloading several operators at once
body: <p>I have a custom class and I want to overload several artihmetic operators, and wonder if there is a way to avoid having to write out the code for each one individually.  I haven't been able to find any examples that don't explicity overload each operator one-by-one.</p>
  
  <pre><code>class Foo(object):
      a=0 
  
      def __init__(self, a):
          self.a=a            
  
      def __add__(self, other):
          #common logic here
          return Foo(self.a+other.a)
  
      def __sub__(self, other):
          #common logic here  
          return Foo(self.a-other.a)
  
      def __mul__(self, other):
          #common logic here
          return Foo(self.a*other.a)
  
  #etc...
  </code></pre>
  
  <p>The logic is slightly more complex than this, but the common pattern is that each operator overload method contains some identical code to check that the operation is allowed, and then constructs an operation using the class members. I want to reduce the redundant code.  This works: </p>
  
  <pre><code>class Foo(object):
      a=0 
  
      def __init__(self, a):
          self.a=a            
  
      def operate(self, other, operator):
          #common logic here
          a = constructOperation(self.a, other.a, operator)
          return Foo(a)
  
      def __add__(self, other):
          return self.operate(other, "+")
  
      def __sub__(self, other):       
          return self.operate(other, "-")     
  
  
  def constructOperation(operand0, operand1, operator):
      if operator=="+": 
          return operand0 + operand1
      if operator=="-": 
          return operand0 - operand1
  </code></pre>
  
  <p>But it seems kind of silly to be constructing operations manually like that. Does this approach make sense, or is there a better way here? </p>