Think Python - Denison University

17.12. Exercises 167object-oriented programming: Astyleofprogramminginwhichdataandtheoperationsthatmanipulateitareorganized intoclasses and methods.method: Afunctionthatisdefinedinsideaclassdefinitionandisinvokedoninstancesofthatclass.subject: The object amethod isinvoked on.operator overloading: Changingthebehaviorofanoperatorlike+soitworkswithauser-definedtype.type-based dispatch: A programming pattern that checks the type of an operand and invokes differentfunctions for different types.polymorphic: Pertaining toafunction that can work withmorethan one type.17.12 ExercisesExercise17.6 Thisexerciseisacautionarytaleaboutoneofthemostcommon,anddifficulttofind,errorsinPython.1. Writeadefinition foraclass namedKangaroowiththefollowing methods:(a) An __init__ method that initializes an attribute named pouch_contents to an emptylist.(b) A method named put_in_pouch that takes an object of any type and adds it topouch_contents.(c) A __str__ method that returns a string representation of the Kangaroo object and thecontents of thepouch.Test your code by creating two Kangaroo objects, assigning them to variables named kangaandroo,and then addingrootothecontents ofkanga’spouch.2. Downloadthinkpython.com/code/BadKangaroo.py. Itcontainsasolutiontothepreviousproblem withone big, nastybug. Findand fixthe bug.If you get stuck, you can download thinkpython.com/code/GoodKangaroo.py, which explainstheproblem and demonstrates asolution.Exercise 17.7 Visual is a Python module that provides 3-D graphics. It is not always included in aPythoninstallation,soyoumighthavetoinstallitfromyoursoftwarerepositoryor,ifit’snotthere,fromvpython.org.The following example creates a 3-D space that is 256 units wide, long and high, and sets the“center” tobe thepoint (128,128,128). Then itdraws a bluesphere.from visual import *scene.range = (256, 256, 256)scene.center = (128, 128, 128)color = (0.1, 0.1, 0.9) # mostly bluesphere(pos=scene.center, radius=128, color=color)