object-oriented programming getter method by the @property decorator the other two are set up by python so that they do nothing (so the attribute cannot be written to or deleted)unless they are used as decoratorsin which case they in effect replace themselves with the method they are used to decorate the circle' initializercircle __init__()includes the statement self radius radiusthis will call the radius property' setterso if an invalid radius is given when circle is created an assertionerror exception will be raised similarlyif an attempt is made to set an existing circle' radius to an invalid valueagain the setter will be called and an exception raised the docstring includes doctests to test that the exception is correctly raised in these cases (testing is covered more fully in both the point and circle types are custom data types that have sufficient functionality to be useful most of the data types that we are likely to create are like thisbut occasionally it is necessary to create custom data type that is complete in every respect we will see examples of this in the next subsection creating complete fully integrated data types |when creating complete data type two possibilities are open to us one is to create the data type from scratch although the data type will inherit object (as all python classes do)every data attribute and method that the data type requires (apart from __new__()must be provided the other possibility is to inherit from an existing data type that is similar to the one we want to create in this case the work usually involves reimplementing those methods we want to behave differently and "unimplementingthose methods we don' want at all in the following subsubsection we will implement fuzzybool data type from scratchand in the subsubsection after that we will implement the same type but will use inheritance to reduce the work we must do the built-in bool type is two-valued (true and false)but in some areas of ai (artificial intelligence)fuzzy booleans are usedwhich have values corresponding to "trueand "false"and also to intermediates between them in our implementations we will use floating-point values with denoting false and denoting true in this system means percent trueand means percent trueand so on here are some usage examples (they work the same with either implementation) fuzzybool fuzzybool fuzzybool fuzzybool > bool( )bool( ~ returnstrue returns(truefalsereturnsfuzzybool(