Contents:

• Overview
• Newly Introduced Techniques
• Collaboration Policy
• Revisiting Our Earlier Work
• Requirements
• Advice About Coordinate Systems
• Submitting Your Assignment
• Extra Credit

Overview

In an earlier assignment, Artist, you created an animation which included several animals. At that time, you relied on the use of the class, Layer, to manipulate your animal as a single coherent unit, rather than as a scattered collection of individual shapes. We saw several advantages in that representation of an animal, such as being able to easily move the animal in the scene.

That use of the class Layer was a step in the right direction, but this time we would like to go a step further, having you create and document a new class which represents your specific animal.

Newly Introduced Techniques

• Using Inheritance

Collaboration Policy

For this assignment you must work individually in regard to the design and implementation of your project.

Please make sure you adhere to the policies on academic integrity in this regard.

Revisiting Our Earlier Work

For the sake of discussion, let's suppose that my original Artist submission has generated an animation which included several monkeys. Presumably my code included some 30-40 lines of code specifically for modeling the monkey. I probably instantiated various shapes to represent the arms, legs and tail of the monkey, as well as instantiating a new Layer to represent the monkey as a whole. Then the body parts were added to the layer, and the layer was added to the canvas.

    chimp = Monkey()
    chimp.move(80,120)
    chimp.scratch()
    paper.add(chimp)

This is our goal. Of course, there is no reason to reinvent the wheel; we do not wish to create our new class entirely from scratch. We have already seen that the concept of a Layer is a great model for representing a Monkey, and so we will use inheritance to define a Monkey as a subclass of Layer. Therefore, we might start out our class definition using syntax such as:

from cs1graphics import *

class Monkey(Layer):
    ...

In this way, any object from class Monkey inherits all of the instance variables and methods associated with the class Layer, such as move(), draw(), setDepth() and so on. Of course, if we do not add any additional code to the class definition for Monkey, then our class will be identical to that of a Layer. Presumably, new instance variables and behaviors may be added, and existing behaviors might be specialized.

Requirements

There are three distinct directions of work which are required for your submission.

1. Create a new class, representing a type of animal.

   In this assignment description, we have been using the discussion of a class Monkey purely for example. Your project should involve the development of a new class to represent your own choice of animal, most likely an animal used in your original Artist project (though you are free to change your mind).

   Please adhere strictly to the following minimum requirements for the development of such a class:

   • You will need to write a constructor which appropriately initializes a newly created animal. Presumably, this will involve the creation and placement of several underlying shapes, which are then added to the animal using the inherited method add().

     You may decide whether or not to allow additional parameters when calling the constructor which effect the initial settings for your animal.

   • Think carefully about the geometry from the perspective of the user. That is, if they execute, chimp.moveTo(100,100), hopefully the monkey is moved visually to that location with a meaningful reference point. That is, perhaps the bottom of the foot is moved there, or the nose, but it should not be that the monkey is played halfway across the screen. In similar respect, rotate and scale are based upon the notion of the reference point, so consider how you define the reference point of one of your instance (by default, it is at coordinate (0,0) of the Layer).

   • All monkeys are not alike! The point of such a class is not simply to make precise clones of an animal, but to allow reasonable variance as well. For example, I might allow a user to change the eye color of a monkey, the tail thickness, the positioning of the arms, the direction of the face.

     Specifically, you must define at least three new (and distinct) methods which are appropriate for customizing your chosen animal.

2. Properly document all aspects of your newly defined animal class.

   For someone else to know how to use your class, you must provide sufficient documentation. For this, we would like you to use docstrings, as described in earlier work. Specifically, please ensure that:

   • You provide a docstring to begin the class definition, which gives an overview of the class as a whole.

   • Any method which you create should begin with an appropriate docstring, giving an overview of the behavior, as well as explicit descriptions of any parameters or return values.

   • The constructor documentation should give sufficient explanation of the initial geometry so that a user could properly place on of these instances into a scene.

3. Provide a Unit Test which demonstrates the use of your class.

   Here, the goal is to show how your class could be used by another. So provide a construct of the form:

   if __name__ == '__main__':
   

   as the final thing in your source code, where the body of the construct demonstrates the use of your class.

   Your animation for this assignment does not need to correspond to the precise animation you created in the original Artist assignment. However, we would like your new animation to satisfy the following requirements:

   • Demonstrate the use of each new method introduced in your class.

   • Display at least four distinct animals from your new class, making sure that the properties vary among those animals.

Advice About Coordinate System

Please keep in mind that the default reference point for a Layer is at (0,0) of the layer's coordinate system. Therefore, this is the default reference point for your shape. Please think carefully about designing your geometry relative to that point. Is there a natural point in your animal's geometry to serve as a reference point? When a user calls a method such as moveTo(100,100) where will this cause your animal to go? Also, the reference point is important for the inherited scale and rotate commands.

Submitting Your Assignment

You should create a new file, appropriately names, which contains all of your own code. This file must be submitted electronically.

You should also submit a separate 'readme' text file, as outlined in the general webpage on programming assignments.

Please see details regarding the submission process from the general programming web page, as well as a discussion of the late policy.

Extra Credit

I'll know it when I see it.