In Python you can override an operation for your class (say, addition) by defining __add__. This will make it possible add class instance with other values/instances, but you can't add built-ins to instances:
foo = Foo() bar = foo + 6 # Works bar = 6 + foo # TypeError: unsupported operand type(s) for +: 'int' and 'Foo' Is there any way to make enable this?
You have to define the method __radd__(self, other) to override the operator + when your instance is on the right side.
__add__(), catch the exception, and then look for __radd__().You cannot override the + operator for integers. What you should do is to override the __radd__(self, other) function in the Foo class only. The self variable references a Foo instance, not an integer, and the other variable references the object on the left side of the + operator. When bar = 6 + foo is evaluated, the attempt to evaluate 6.__add__(foo) fails and then Python tries foo.__radd__(6) (reverse __add__). If you override __radd__ inside Foo, the reverse __add__ succeeds, and the evaluation of 6 + foo is the result of foo.__radd__(6).
def __radd__(self, other): return self + other 
other variable references the object on the right side but it should be on the left side.