This lab exercise provides practice with class inheritance in Python.
You will work with a partner on this exercise during your lab session. Two people should work at one
computer. Occasionally switch the person who is typing. Talk to each other about what you are doing
and why so that both of you understand each step.
1. Examine the file named “lab14.py”, which contains a simple test bed for the classes in “pets.py”, and
then execute the test bed.
2. Examine the file named “pets.py”, which contains an outline of four classes to support the handling
of pets within Python programs.
Please note that class “PetError” is a subclass of class “Exception” and is complete as-is. You will
complete the remaining three classes as described below.
Class “Pet” (which is a subclass of class “Object”) should include the following methods:
__init__ Accepts three arguments: self, species (default None), and name (default “”). Stores
species and name as data attributes. Raises PetError if species is not one of the
following (case insensitive): 'dog', 'cat', 'horse', 'gerbil', 'hamster', 'ferret'.
__str__ Returns a string which depends on whether the pet is named or not.
if named: "Species of: Xxx, named Yyy", where Xxx is the species data attribute and Yyy is the
name data attribute, both in “title-case” (first letter upper case and rest lower case).
otherwise: "Species of: Xxx, unnamed", where Xxx is the species data attribute in “title-case”.
Class “Dog” (which is a subclass of class “Pet”) should include the following methods:
__init__ Accepts three arguments: self, name (default “”), and chases (default “Cats”). Uses the
constructor for class “Pet” to store species (“Dog”) and name as data attributes. Stores
chases as a data attribute.
__str__ Returns a string which depends on whether the dog is named or not.
if named: "Species of: Dog, named Yyy, chases zzz", where Yyy is the name data attribute (as
above) and zzz is the chases data attribute.
otherwise: "Species of: Dog, unnamed, chases zzz", where zzz is the chases data attribute.Class “Cat” (which is a subclass of class “Pet”) should include the following methods:
__init__ Accepts three arguments: self, name (default “”), and hates (default “Dogs”). Uses the
constructor for class “Pet” to store species (“Cat”) and name as data attributes. Stores
hates as a data attribute.
__str__ Returns a string which depends on whether the dog is named or not.
if named: "Species of: Cat, named Yyy, hates zzz", where Yyy is the name data attribute (as
above) and zzz is the hates data attribute.
otherwise: "Species of: Cat, unnamed, hates zzz", where zzz is the hates data attribute.
3. Revise the methods within class “Pet” to accomplish the required tasks.
4. Revise the methods within class “Dog” and class “Cat” to accomplish the tasks required tasks.
5. Revise the test bed to demonstrate that all of the methods in those three classes are correct. Be sure
to demonstrate the use of default argument values and error conditions.
Demonstrate your completed program to your TA. On-line students should submit the
completed files (named “lab14.py” and “pets.py”) for grading via the CSE handin system.