The __radd__ method

__radd__(self, other)

These methods are called to implement the binary arithmetic operations (+, -, \*, /, %, divmod(), pow(), \*\*, <``<, ` >`>, &, ^, |) with reflected (swapped) operands. These functions are only called if the left operand does not support the corresponding operation. For instance, to evaluate the expression x-y, where y is an instance of a class that has an __rsub__() method, y.\_\_rsub\_\_(x) is called. Note that ternary pow() will not try calling __rpow__() (the coercion rules would become too complicated).