using graphical objects some of the examples in the above interactions may look bit strange to you to really understand the graphics modulewe need to take an object-oriented point of view rememberobjects combine data with operations computation is performed by asking an object to carry out one of its operations in order to make use of objectsyou need to know how to create them and how to request operations in the interactive examples abovewe manipulated several different kinds of objectsgraphwinpointcircleovallinetextand rectangle these are examples of classes every object is an instance of some classand the class describes the properties the instance will have borrowing biological metaphorwhen we say that fido is dogwe are actually saying that fido is specific individual in the larger class of all dogs in oo terminologyfido is an instance of the dog class because fido is an instance of this classwe expect certain things fido has four legsa taila coldwet nose and he barks if rex is dogwe expect that he will have similar propertieseven though fido and rex may differ in specific details such as size or color the same ideas hold for our computational objects we can create two separate instances of pointsay and each of these points has an and valueand they both support the same set of operations like getx and draw these properties hold because the objects are points howeverdifferent instances can vary in specific details such as the values of their coordinates to create new instance of classwe use special operation called constructor call to constructor is an expression that creates brand new object the general form is as follows(here is the name of the class that we want to create new instance ofe circle or point the expressions in the parentheses are any parameters that are required to initialize the object the number and type of the parameters depends on the class point requires two numeric valueswhile graphwin can be constructed without any parameters oftena constructor is used on the right side of an assignment statementand the resulting object is immediately assigned to variable on the left side that is then used to manipulate the object to take concrete examplelet' look at what happens when we create graphical point here is constructor statement from the interactive example above point( , the constructor for the point class requires two parameters giving the and coordinates for the new point these values are stored as instance variables inside of the object in this casepython creates an instance of point having an value of and value of the resulting point is then assigned to the variable conceptual diagram of the result is shown in figure note thatin this diagram as well as similar ones later ononly the most salient details are shown points also contain other information such as their color and which window (if anythey are drawn in most of this information is set to default values when the point is created to perform an operation on an objectwe send the object message the set of messages that an object responds to are called the methods of the object you can think of methods as functions that live inside of the object method is invoked using dot-notation