lab06 : Sorting Apartments

Introduction

In this lab, you’ll have the opportunity to practice:

• Defining classes in Python
• Overloading the ==, <, and > operators in a Python class
• Implementing an O(n log n) mergesort on a list of Apartment objects
• Writing functions that ensure the list of Apartment objects are in sorted order
• Determining the best/worst apartment in a list
• Listing out all of the apartments that are affordable
• Testing your functionality with pytest

Note: It is important that you start this lab early so you can utilize our office hours to seek assistance / ask clarifying questions during the week before the deadline if needed!

For this lab, you have been hired as a realtor for an up-and-coming property management company located in Isla Vista. You are tasked with renting out as many apartments as you can. In order to do so, you will write a program that will sort apartment objects. You have decided that the three most important properties of an Apartment object are its rent, meters from UCSB, and condition. You have decided to sort Apartments as follows. First, you will organize the Apartment by increasing rent. In the event of a tie (several Apartments have the same rent), the meters from UCSB will be used to determine the Apartment’s place in the list. The closer the apartment is to campus, the better. If the rent and the meters from campus are the same, then the Apartment’s condition will be used to determine the Apartment’s place in the list. An apartment can have either a "bad", "average", or "excellent" condition - the better the condition is, the better the apartment. You may assume that apartment objects will have either "bad", "average", or "excellent" as their condition when comparing / sorting apartments.

This lab will require you to define an Apartment class and create the file lab06.py. Note that labO6.py is not a class.

Instructions

You will need to create three files:

• Apartment.py - file containing a class definition for an Apartment object
• lab06.py - file containing mergesort and other functions defined in the lab06.py section of this lab.
• testFile.py - file containing pytest functions testing the overall correctness of your class definitions

There will be no starter code for this assignment, but rather the class descriptions and required methods are defined in the specification below.

You should organize your lab work in its own directory. This way all files for a lab are located in a single folder. Also, this will be easy to import various files into your code using the import / from technique shown in lecture.

Apartment.py class

The Apartment.py file will contain the definition of an Apartment. We will define the Apartment attributes as follows:

• rent - integer that represents the rent of the Apartment
• meters_from_UCSB - integer that represents the Apartment’s distance, in meters, from UCSB
• condition - string that represents the condition of the Apartment. This string will be one of three options: "bad", "average", or "excellent".

You should write a constructor that allows the user to construct an apartment object by passing in values for all of the fields. You may assume that all attributes of the Apartment object will be defined. Therefore, there should be no default values for rent, metersFromUCSB, or condition.

• __init__(self, rent, meters_from_UCSB, condition)

In addition to your constructor, your class definition should also support “getter” methods that can receive the state of the Apartment object:

• get_rent(self)
• get_meters_from_UCSB(self)
• get_condition(self)

You will also implement the method

• get_apartment_details(self)

that returns a str with all of the Apartment attributes. The string should contain all attributes in the following EXACT format (Note: There is no \n character at the end of this string):

a0 = Apartment(1204, 200, "bad")
print(a0.get_apartment_details())

Output

(Apartment) Rent: $1204, Distance From UCSB: 200m, Condition: bad

• Lastly, your Apartment class should overload the >,<, and == operators. This will be used when finding the proper position of an Apartment in the list using the specifications (first by rent, then distance and then condition) in the Introduction section of this lab. In this context for example, the < operator will return True for Apartment1 < Apartment2 if Apartment1 is better than Apartment2. We reviewed operator overloading in class and the textbook does discuss overloading Python operators. You can also refer to this reference on overloading various operators as well:

https://www.geeksforgeeks.org/operator-overloading-in-python/

lab06.py

This file will contain functions that sort a list of Apartment objects, ensures that the list of Apartment objects are in asending order (best-to-worst), retrives information about the best/worst apartments, and gets the info of every affordable apartment in the list. These function defintions as well as their descriptions are provided below. Note that in order for the autograder to correctly check your implementation, function defintions must match exactly.

• merge_sort(apartmentList) - Performs a mergesort on the apartmentList passed as input. Sorts the Apartment objects based on the specifications in the Introduction section of this lab. Gradescope will test to ensure that your mergesort implementation’s Big-O is O(NlogN). You may refer to the implementation given in the textbook.
• ensure_sorted_ascending(apartmentList) - method that returns a boolean value. True if the apartmentList is sorted correctly in asending order. False otherwise.
• get_best_apartment(apartmentList) - method that returns a string detailing the best Apartment’s rent, meters from UCSB, and condition. Make use of get_apartment_details(self) and merge_sort(apartmentList). You can assume that apartmentList has at least one apartment.
• get_worst_apartment(apartmentList) - method that returns a string detailing the worst Apartment’s rent, meters from UCSB, and condition. Make use of get_apartment_details(self) and merge_sort(apartmentList). You can assume that apartmentList has at least one apartment.
• get_affordable_apartments(apartmentList, budget) - method that returns a labeled, newline separated string detailing the rent, meters from UCSB, and condition of all the apartments whose rent is less than or equal to budget from the apartmentList in sorted order. Make use of get_apartment_details(self) and merge_sort(apartmentList). Note: You can assume that apartmentList has at least one apartment and that there is no newline at the end of the string returned by this method. If there are no apartments that are affordable in the apartmentList, this method returns an empty string.

Sample Output 1

a0 = Apartment(1115, 215, "bad")
a1 = Apartment(950, 215, "average")
a2 = Apartment(950, 215, "excellent")
a3 = Apartment(950, 190, "excellent")
a4 = Apartment(900, 190, "excellent")
a5 = Apartment(500, 250, "bad")
apartmentList = [a0, a1, a2, a3, a4, a5]


print('apartmentList is NOT SORTED:')
for apartment in apartmentList: 
    print(apartment.get_apartment_details())

assert ensure_sorted_ascending(apartmentList) == False
merge_sort(apartmentList)
assert ensure_sorted_ascending(apartmentList) == True

print('apartmentList is SORTED:')
for apartment in apartmentList: 
    print(apartment.get_apartment_details())

Output:

apartmentList is NOT SORTED:
(Apartment) Rent: $1115, Distance From UCSB: 215m, Condition: bad
(Apartment) Rent: $950, Distance From UCSB: 215m, Condition: average
(Apartment) Rent: $950, Distance From UCSB: 215m, Condition: excellent
(Apartment) Rent: $950, Distance From UCSB: 190m, Condition: excellent
(Apartment) Rent: $900, Distance From UCSB: 190m, Condition: excellent
(Apartment) Rent: $500, Distance From UCSB: 250m, Condition: bad
apartmentList is SORTED:
(Apartment) Rent: $500, Distance From UCSB: 250m, Condition: bad
(Apartment) Rent: $900, Distance From UCSB: 190m, Condition: excellent
(Apartment) Rent: $950, Distance From UCSB: 190m, Condition: excellent
(Apartment) Rent: $950, Distance From UCSB: 215m, Condition: excellent
(Apartment) Rent: $950, Distance From UCSB: 215m, Condition: average
(Apartment) Rent: $1115, Distance From UCSB: 215m, Condition: bad

Sample Output 2

a0 = Apartment(1200, 200, "average")
a1 = Apartment(1200, 200, "excellent")
a2 = Apartment(1000, 100, "average")
a3 = Apartment(1000, 215, "excellent")
a4 = Apartment(700, 315, "bad")
a5 = Apartment(800, 250, "excellent")
apartmentList = [a0, a1, a2, a3, a4, a5]

assert ensure_sorted_ascending(apartmentList) == False

print('Best Apartment in apartmentList:')
print(get_best_apartment(apartmentList))

print('Worst Apartment in apartmentList:')
print(get_worst_apartment(apartmentList))

Output:

Best Apartment in apartmentList: 
(Apartment) Rent: $700, Distance From UCSB: 315m, Condition: bad
Worst Apartment in apartmentList:
(Apartment) Rent: $1200, Distance From UCSB: 200m, Condition: average

Sample Output 3

a0 = Apartment(1115, 215, "bad")
a1 = Apartment(970, 215, "average")
a2 = Apartment(950, 215, "average")
a3 = Apartment(950, 190, "excellent")
a4 = Apartment(900, 190, "excellent")
a5 = Apartment(500, 250, "bad")
apartmentList = [a0, a1, a2, a3, a4, a5]

print('All apartments whose rent is <= in SORTED order:')
print(get_affordable_apartments(apartmentList, 950))

Output:

All apartments whose rent is <= in SORTED order:
(Apartment) Rent: $500, Distance From UCSB: 250m, Condition: bad
(Apartment) Rent: $900, Distance From UCSB: 190m, Condition: excellent
(Apartment) Rent: $950, Distance From UCSB: 190m, Condition: excellent
(Apartment) Rent: $950, Distance From UCSB: 215m, Condition: average

A Brief Note on Sorting Apartments

A common question that students have when working through this lab is

The directions say that a0 < a1 should return true if apartment a0 is a better apartment than a1. Intuitively though, why would the apartment that is lesser (<) be “better than” the other apartment?

Recall that you are sorting apartments in ascending order. For example, if you sorted runners in a race by the position they finished in you would do something like this:

1 4 3 2 5 —> 1 2 3 4 5

It is clear that 1<2, 2<3 etc. Notice that the 1st place runner finished in a “better” position even though they have a “lesser” position than the others. The same concept applies here to apartments.

How to Best Approach This Lab

There are a lot of parts to this lab that rely on one another. So if you’re failing a test and find yourself stuck it might be because of code that you’ve written elsewhere. To alleviate some of this stress, here are the suggested order in which you complete the functions required for this lab:

1. constructor and getters in Apartment.py
2. get_apartment_details in Apartment.py
3. <, >, and == overloaded operators in Apartment.py
4. ensure_sorted_ascending in lab06.py
5. merge_sort in lab06.py
6. get_best_apartment and get_worst_apartment in lab06.py
7. get_affordable_apartments in lab06.py

testFile.py pytest

This file should import your Apartment.py class and your lab06.py function. You should write tests using pytest to test if the functionality is correct. Think of various scenarios and edge cases when testing your code. Write your tests first in order to check the correctness of the Apartment and then lab06.py methods. Gradescope requires testFile.py to be submitted before running any autograded tests. You should write at least one test for each method in each of these classes. This includes the overloaded operators but excludes the getters.

Submission

Once you’re done with writing your recursive function definitions and tests, submit your Apartment.py and lab06.py to the Lab06 assignment on Gradescope. There will be various unit tests Gradescope will run to ensure your code is working correctly based on the specifications given in this lab. There also will be tests to ensure that your mergesort in lab06.py runs in O(n log n) time. Note that if your autograder seems to be running for a really long time, your mergesort does not run O(NlogN).

If the tests don’t pass, you may get some error message that may or may not be obvious at this point. Don’t worry - if the tests didn’t pass, take a minute to think about what may have caused the error. If your tests didn’t pass and you’re still not sure why you’re getting the error, feel free to ask your TAs or Learning Assistants.

^{* Lab06 created by Gautam Mundewadi and adapted / updated by Richert Wang (F23) and Prof K (W24)}