Unary operators are operators which work only on the object itself, so not in combination with another object. A typical example is using the minus (-) sign in front of a number to turn it into a negative number. You can overload some of the unary operators, and also some of the basic functions that work on an object.

• __neg__() implements the negation (-) of an object

• __pos__() implements placing a plus (+) in front of an object (usually without effect)

• __invert__() implements the bitwise not (\~)

• __abs__() implements taking the object’s absolute value when using the abs() function

• __int__() implements taking the (rounded down) integer value of an object when using the int() function; must return an integer

• __float__() implements taking the floating-point value of an object when using the float() function; must return a float

• __round__() implements rounding using the round() function. An optional second argument can be given to specify the number of decimals; must return an integer or a float

• __bytes__() implements representing the object as a byte string. It is in that respect similar to the __str__() method which was discussed in Chapter 21¹

class Quaternion:
    def __init__( self, a, b, c, d ):
        self.a, self.b, self.c, self.d = a, b, c, d
    def __repr__( self ):
        return "({},{}i,{}j,{}k)".format( self.a, self.b, 
            self.c, self.d )
    def __neg__( self ):
        return Quaternion( -self.a, -self.b, -self.c, -self.d)
    def __abs__( self ):
        return Quaternion( abs( self.a ), abs( self.b ), 
            abs( self.c ), abs( self.d ) )
    def __bytes__( self ):
        return self.__str__().encode( "utf-8" )

c1 = Quaternion( 3, -4, 5, -6 )
print( c1 )
print( -c1 )
print( abs( c1 ) )
print( bytes( c1 ) )

Note

You might think it would be a good idea to also implement the __int__(), __float__(), and __round__() methods, that, respectively, use the int(), float(), and round() functions on self.a, self.b, self.c, and self.d. Unfortunately, that cannot be done, as these methods must return integers or floats, and not Quaternions. Other than what I propose, I see no sensible interpretation of int(), float(), and round() for Quaternion, so these methods should not be implemented.