HW: Introduction to Classes

Objective: Learn how to create and use classes, add methods, validate input, and practice inheritance.

In this assignment, you will complete a three-part exercise. In Part 1, you will create a Material class for tracking construction materials. In Part 2, you will create a ConstructionProject class that manages a project with multiple materials and labor costs. In Part 3, you will use inheritance to create a RoadProject class that extends ConstructionProject with road-specific attributes and methods.

Getting Started

1. First, make a copy of the starter sheet here:

2. Rename it something like "(Your_Name)_HW_Intro_Classes.ipynb".

---

Part 1 - Material Class

In this part, you will create a class called Material that represents a construction material (e.g., concrete, rebar, lumber). This class will track the material's name, cost, unit of measurement, and quantity.

1. In Code Block 1, define a class called Material with an __init__ method that takes the following parameters:

   Parameter	Description	Default
   name	Name of the material (e.g., "Concrete")	None
   unit_cost	Cost per unit (e.g., 125.00)	None
   unit	Unit of measure (e.g., "cubic yards")	None
   quantity	Amount of material on hand	0

2. Add validation in the __init__ method:

   • If unit_cost is less than or equal to 0, print an error message and set unit_cost to 1.
   • If quantity is less than 0, print an error message and set quantity to 0.

3. Add a method called total_cost() that returns unit_cost * quantity.

4. Add a method called add_quantity(amount) that adds the given amount to the current quantity. If the amount is less than or equal to 0, print an error message and do not change the quantity.

5. Add a method called use_quantity(amount) that subtracts the given amount from the current quantity. If the amount is greater than the current quantity, print an error message that includes the material name and current quantity, and do not change the quantity. If the amount is less than or equal to 0, print an error message.

6. Add a print_description method that returns a formatted string like:

Concrete: 50 cubic yards @ $125.00/cubic yards = $6,250.00

7. Test your Material class in the Code Block 1 Test cell by doing the following: - Create a material and print it. - Add quantity using the add_quantity() method and print it. - Use quantity using the use_quantity() method and print it. - Try to use more quantity than available with the use_quantity() method.

Your output should look similar to this:

Concrete: 50 cubic yards @ $125.00/cubic yards = $6,250.00
After adding 20: Concrete: 70 cubic yards @ $125.00/cubic yards = $8,750.00
After using 30: Concrete: 40 cubic yards @ $125.00/cubic yards = $5,000.00
Error: Not enough Concrete available. Current quantity: 40 cubic yards.

---

Part 2 - ConstructionProject Class

In this part, you will create a class called ConstructionProject that manages a construction project. It will use Material objects from Part 1 to track materials and calculate costs.

1. In Code Block 2, define a class called ConstructionProject with an __init__ method that takes the following parameters:

   Parameter	Description	Default
   project_name	Name of the project	None
   budget	Total project budget in dollars	None
   labor_rate	Labor cost per hour in dollars	None

2. In __init__, also initialize the following attributes:

   • materials as an empty list (this will hold Material objects)
   • hours_worked as 0

3. Add a method called add_material(material) that appends a Material object to the materials list.

4. Add a method called log_hours(hours) that adds hours to hours_worked. If hours is less than or equal to 0, print an error message.

5. Add a method called total_material_cost() that loops through all materials in the materials list and returns the sum of each material's total_cost().

6. Add a method called total_labor_cost() that returns labor_rate * hours_worked.

7. Add a method called total_project_cost() that returns the sum of total_material_cost() and total_labor_cost().

8. Add a method called is_under_budget() that returns True if total_project_cost() is less than or equal to budget, and False otherwise.

9. Add a method called summary() that prints a formatted project summary. The summary should include:

   • Project name and budget
   • A list of all materials (use each material's print_description method)
   • Total material cost
   • Labor hours, rate, and total labor cost
   • Total project cost
   • Remaining budget (budget minus total project cost)
   • Whether the project is under or over budget

10. Test your ConstructionProject class in the Code Block 2 Test cell by doing the following:

    • Create three materials (concrete, rebar, and lumber) using the Material class.
    • Create a project using the ConstructionProject class you just created.
    • Add the three materials to the project using the add_material() method.
    • Log hours using the log_hours() method.
    • Print the summary using the summary() method.

    Use the following test data:

    Material	Unit Cost	Unit	Quantity
    Concrete	125.00	cubic yards	50
    Rebar	0.85	lbs	5000
    Lumber	6.50	board feet	2000

    Project	Budget	Labor Rate	Hours
    Campus Parking Garage	500,000.00	45.00	1200

Your output should look similar to this:

--- Project Summary: Campus Parking Garage ---
Budget: $500,000.00
Materials:
  - Concrete: 50 cubic yards @ $125.00/cubic yards = $6,250.00
  - Rebar: 5000 lbs @ $0.85/lbs = $4,250.00
  - Lumber: 2000 board feet @ $6.50/board feet = $13,000.00
Total Material Cost: $23,500.00
Labor: 1200 hours @ $45.00/hr = $54,000.00
Total Project Cost: $77,500.00
Remaining Budget: $422,500.00
Status: UNDER BUDGET

---

Part 3 - RoadProject (Inheritance)

In this part, you will create a class called RoadProject that inherits from ConstructionProject. This class adds road-specific attributes and methods while reusing all the functionality from the parent class.

1. In Code Block 3, define a class called RoadProject that inherits from ConstructionProject. The __init__ method should take the following parameters:

   Parameter	Description	Default
   project_name	Name of the road project	None
   budget	Total project budget in dollars	None
   labor_rate	Labor cost per hour in dollars	None
   length_miles	Length of the road in miles	None
   num_lanes	Number of lanes	None

   Use super().__init__() to call the parent class constructor with project_name, budget, and labor_rate. Then set length_miles and num_lanes as additional attributes.

2. Add a method called cost_per_mile() that returns the total project cost divided by length_miles.

3. Add a method called cost_per_lane_mile() that returns cost_per_mile() divided by num_lanes.

4. Override the summary() method to print a road-specific summary. It should include everything from the original summary plus:

   • Road length and number of lanes
   • Cost per mile
   • Cost per lane-mile

5. Test your RoadProject class in the Code Block 3 Test cell by doing the following:

   • Create three materials (asphalt, gravel, and rebar) using the Material class.
   • Create a road project using the inherited RoadProject class.
   • Add the three materials to the project using the add_material() method.
   • Log hours using the log_hours() method.
   • Print the summary using the summary() method.

   Use the following test data:

   Material	Unit Cost	Unit	Quantity
   Asphalt	95.00	tons	800
   Gravel	28.00	tons	1500
   Rebar	0.85	lbs	20000

   Project	Budget	Labor Rate	Hours	Length	Lanes
   Highway 89 Expansion	2,000,000.00	52.00	5000	3.5	4

Your output should look similar to this:

--- Road Project Summary: Highway 89 Expansion ---
Road: 3.5 miles, 4 lanes
Budget: $2,000,000.00
Materials:
  - Asphalt: 800 tons @ $95.00/tons = $76,000.00
  - Gravel: 1500 tons @ $28.00/tons = $42,000.00
  - Rebar: 20000 lbs @ $0.85/lbs = $17,000.00
Total Material Cost: $135,000.00
Labor: 5000 hours @ $52.00/hr = $260,000.00
Total Project Cost: $395,000.00
Cost per Mile: $112,857.14
Cost per Lane-Mile: $28,214.29
Remaining Budget: $1,605,000.00
Status: UNDER BUDGET

---

Turning in/Rubric

REMINDER - For this class, you will only turn in the links to your colab notebooks. You will get a 0 for this assignment if you turn in a python file or a link that is not correct, wrong assignment, or does not give editor permission.

Rubric:

Item	Amount
Material __init__ with validation is correct	2
total_cost() method works correctly	2
add_quantity() method works correctly	2
use_quantity() with validation works correctly	2
project_description method returns formatted string	2
ConstructionProject __init__ is correct	2
add_material() and log_hours() work correctly	2
total_material_cost() loops and sums correctly	2
total_labor_cost() and total_project_cost() correct	2
is_under_budget() returns correct boolean	1
summary() prints formatted output	3
RoadProject inherits from ConstructionProject	2
super().__init__() used correctly	2
cost_per_mile() and cost_per_lane_mile() correct	2
summary() override includes road-specific info	3
Total	31

---

The following is not a part of the rubric, but specifies how you can lose points. For example: if you do not explain your code when using AI to help you create it or fail to share your link correctly.

Reasons for Points Lost	Amount
Link shared incorrectly	-10%
Turned in late (per week)	-10% (up to -50%)
No comments explaining where AI is used and what its provided code does	-50%